GOB (most meanings of this word are unpleasant, and I’m not sure how it corresponds to “shot”, but perhaps both could be a mouthful of drink?) + S (abbreviation for son) + TOPPER (top hat, usually black). CORRECTION: thanks to Kurukveera @1. It’s GO (shot = attempt), then S (abbreviation for son) inserted into B (black) + TOPPER (top hat).

GOBSTOPPER