|Credit: Ghost of a Flea blog. Your obedient servant often feels like the player with the red pieces.|
The definition of "1 across" is "In chess: giving up pieces for positional advantage in the opening". Yes, they mean "gambit"-- which, incidentally, is the term used in Hebrew as well, the word having become an international one, like "Zugzwang" and similar chess-related words.
One is reminded of Edward Winter's article, Who was R. J. Buckley?, where he quotes Buckley's quip about one of his games with Bird: "The next game was a Muzio, in which we sacrificed several pieces, emerging with an excellent position, but no men."
Perhaps that's what the crossword writer meant. But I wouldn't bet on it.