Leonard Tose, owner of the Philadelphia Eagles, announced yesterday an agreement to sell "a significant interest" in the team, a move that evidently ensures his daughter will become the second woman owner of a National Football League franchise.

Susan Fletcher, as the club's chief operating officer, has been running its nonfootball operations. As part of the investment group buying into the team, she will become managing general partner. Tose, who has been seeking to sell off a minority interest in the team, is chairman of the board.

Tose refused to say how much of the Eagles will be sold to the investment group, which includes Julius Newman, a Philadelphia surgeon; Sandra Schultz Newman, an attorney; Louis P. Guida, a Wall Street investor and syndicator of standout harness horse Niatross, and Ira B. Lampert, managing partner of a major regional accounting firm,

Tose said Fletcher "will end up with the club" and that "we (still) control the club . . . This is a good deal for me, a good deal for Susan. As long as I live, everything will be the same."

Georgia Frontiere is the NFL's only woman owner now. She inherited the Los Angeles Rams from her late husband, Carroll Rosenbloom.

Tose put Fletcher, a lawyer, in charge of the Eagles after the team lost about $5 million during the strike-shortened 1982 season. Fletcher has introduced a number of cost-cutting measures and has fired many long-time front office members, including Jim Murray, a close friend of Tose who was general manager.

"There is no doubt in my mind this club will turn a substantial profit once we recover from the strike," Fletcher said. "It (the strike loss) won't wash away in 1983, but by 1984-85 we should begin to see daylight."

Tose has had constant financial problems since buying the team in 1970 from Jerry Wolman for $16.5 million. The purchase was financed by loans of $6.5 million from a group of private lenders and $10 million from a consortium of banks.

In 1978, the banks canceled their loan, but Charles Sullivan, a New York lawyer whose family owns the New England Patriots, got Tose permanent financing at Citibank in New York. Tose later bought out the private lenders.

But he has had to take out bank loans at high interest rates to keep the team running, and the substantial loss caused by the strike forced him to seek more stable financing. He said he also wanted to finish estate planning, to make sure his daughter would inherit the Eagles.