The chief attorney for Sen. Herman E. Talmadge (D-Ga.) told Senate ethics committee members yesterday that he laid a trap for the senator's former wife, Betty, when she testified Tuesday that Talmadge squirreled away thousands of dollars over the years in an o*ld overcoat.

In her testimony, Betty Talmadge told the Senate Select Committee on Ethics that in January 1974 she removed between $12,000 and $15,000 from the secret cache of funds that she estimated contained up to $45,000. She said the money she took was in an envelope maked with the name "Harry P. Anestos."

But yesterday Talmadge's executive assistant. T. Rogers Wade, in a surprise appearance for the senator's attorneys, said he had written Anestos' name on the envelope 17 months after Mrs. Talmadge said she took it and kept it.

"I wanted Mrs. Talmadge under oath on this particular point - when she got that envelope and what was written on it," said Talmadge attorney James Hamiltion.

Wade said the envelope contained no cash but did have some information about a speech that Anestos, a longtime Talmadge supporter, wanted the senator to make. Wade said he wrote Anestos' name on the outside of the envelope and put it on Talmadge's desk. That was the last he saw it, he said.

Wade's testimony was hedged yesterday with warnings to the committee that he could not verify his recollection and that his memory about the envelope was poor.

In their brief cross-examination of Betty Talmadge Tuesday, the senator's attorneys clearly sought not to duplicate the harsh questioning they unleashed on the other primary witness against Talmadge, his former aide Daniel Minchew. Talmadge's attorneys hammered away for six days at Minchew's credibility and character until they were finally cut short by committee chairman Sen. Adlai E. Stevenson (D-I11).

But the introduction of Wade's testimony yesterday questioning Betty Talmadge's credibility was consistent with the offensive strategy that has been employed by the Talmadge's attorneys throughout the six weeks of hearings.

Talmadge faces five allegations of financial wrongdoing lodged by committee special counsel Carl Eardley last December. None of the charges deals specifically with Betty Talmadge's allegations about the secret hoard of $100 bills. But Minchew has said Talmadge used illegally diverted Senate and campaign money in $100 denominations for his daily expenses.

The Georgia senator has denied Minchew's allegations and has said he paid his day-to-day expenses either by check or with $5 and $10 donations given to him by supporters.

The special counsel has now concluded the case against Talmadge. Hamilton told the committee he would submit a brief today calling for the committee to drop all the charges against Talmadge.

Stevenson said the committee will rule on Talmadge's dismissal motion when the hearings resume Tuesday.