Eating her Thanksgiving turkey in the employe lounge of the Zayre store near Tysons Corner yesterday, Tammy Clem knew she was actually getting her first taste of Christmas in the retail business.

"I worked 46 hours last week and guess it's gonna get worse," said the young cashier, one of thousands of temporary employes added to store payrolls for the month-long shopping spree that starts today.

It's the part-timers and temporaries -- like Clem and fellow cashier Dave Kilpatrick -- who draw the Thanksgiving-day duty and the late-night hours that create a love-hate relationship between shoppers and clerks at Christmas. t

"The customers are real nice today," said Kilpatrick, who gobbled up lunch when Zayre's Turkey Day traffic thinned at mid-afternoon. "It's when there are 10 registers open and a line at every one that everybody starts complaining. It's real bad then."

Working on Thanksgiving isn't so awful, he added, but ahead is the non-stop Marathon Sale when the store will keep its doors open for 36 hours in a row to draw in even more business.

Such midnight madness may not be universal among retailers this year, but aggressive promotion is expected to be common this Christmas.

There's considerable anxiety among merchants this year, but knowledgeable retailers say business has not been bad lately.

"I've heard a lot of gloom and doom, but I don't share that," said Washington shoe store owner Frank Rich. "We are enjoying the best year our business has enjoyed since I can remember."

Rich said he believes putting emphasis on medium-priced merchandise and on items "that are identifiable in terms of what they look like," will keep sales strong in the crucial selling days ahead.

The success of nearly every retailer's year is determined by what happens in the final quarter -- November, December and January. For two years in a row, the fourth quarter has brought a reassuring surge of sales that pushed the final figures ahead of most stores' projections.

But this year there are doubts about whether a similar surge can be counted on, what with soaring heating costs, sluggish auto sales, inevitable inflation and now, the depressing developments in the Middle East.

So, as the weight of the Thanksgiving Day newspapers indicated, most stores will be advertising heavily and cutting prices a little more than usual this season, trying to do all they can to make their own Christmas wishes come true.

For the Hess department store in Frederick, Md., that extra effort will involve a confrontation this Sunday between Santa Claus and the sheriff.

Frederick County is the only remaining place in the whole Washington-Baltimore market that doesn't allow Sunday sales, and Hess has decided to try to break the blue law.

Fred Bentelspacher, sales promotion manager of the Allentown, Pa.-based chain, said Hess will open the store at noon on Sunday despite warnings from the local sheriff and county attorney that they will enforce the law, chain the doors shut and arrest the manager.

Rentelspacher said he's tempted to dress the store manager up as Santa for the showdown, in which thousands of dollars in Christmas business are at stake.

"Twenty miles down (Interstate) 270 in Gaithersburg, they're open. Right across the line in Baltimore County, they're doing business. We surveyed our customers, and we know they go there to shop on Sunday," he said.

The other 17 of the Hess stores are open Sundays he added, and do 15 to 18 percent of their week's business between noon and 6 p.m. "It's the most productive six hours of the whole week as far as sales per hour go. It's the biggest family shopping day of the whole week."