* The proposed merger of American Hospital Supply Corp. and Hospital Corp. of America has received antitrust clearance from the Justice Department, the two companies announced yesterday.

In addition to allowing the merger to proceed if it is approved by shareholders, the clearance allows the two companies to invoke a "stock swap" clause of their merger agreement intended to discourage other bidders. HCA said last week it was ready to go ahead with the swap after Baxter Travenol Laboratories Inc. made a competing bid for American. But a spokesman for Nashville-based HCA, the nation's largest for-profit hospital chain, said yesterday that "no decision has been made" on invoking the swap clause. At American, based in suburban Evanston, Ill., a spokesman said the health-care products distributor and manufacturer also had not made a decision on triggering the stock swap.

On Monday, American and HCA indefinitely postponed shareholder meetings that had been called to vote on their proposed merger. The postponement followed Baxter's revised proposal that strengthened its $3.7 billion bid for American. The Baxter offer is valued at $50 a share in cash and securities, while the American-HCA combination is valued at about $35 a share and involves giving shareholders of the two companies shares in a new holding company.