The Senate easily defeated an attempt yesterday to cut its $7.5 billion toxic-waste cleanup bill by almost $2 billion, rejecting arguments that the higher funding would turn the Superfund program into a "pork barrel" and a "lawyers' relief act."

Voting 79 to 15, the Senate rebuffed a bid by Steve Symms (R-Idaho) to pare the cleanup program to $5.7 billion over five years, slightly more than the $5.3 billion sought by the Reagan administration.

The vote was a strong signal that the Senate intends to approve a broad-based tax on large manufacturers as a way to finance a greatly expanded Superfund, despite veto warnings from the White House.

Symms and Jesse Helms (R-N.C.), arguing for a pared-down program, suggested that the fivefold increase in funds would create a "classic opportunity for pork-barreling" and encourage inadequate cleanups.

"We don't have the money to throw around that this bill calls for," Symms said.

But supporters of the bill said the increase is needed to speed cleanup activity. "We have to do it eventually, and it's only going to get more expensive the longer we put it off," Bob Packwood (R-Ore.) said. "Let's not pretend we're saving any money."

At the heart of the Senate's predicament is the method it has chosen to finance Superfund. The manufacturing tax is essentially a value-added tax, which the administration regards as the most insidious kind of revenue-raising measure.

A special tax on raw petrochemicals provided most of the funding for the current $1.6 billion program, but lawmakers believe that tax cannot be sharply increased without having a severe impact on the petroleum and chemical industries. In debate yesterday, several senators expressed distaste for the value-added tax, but said they would vote for it anyway.

"I have great difficulty in swallowing this, but I see no alternative at the moment," said Howard M. Metzenbaum (D-Ohio), who called the tax "unfair and regressive."

The Senate is expected to give final approval to the bill next week, but several controversial issues remain..

The administration also opposes a demonstration project for compensating victims of toxic waste and wants a provision deleted that allows citizens to sue the government.