Mostly, clankin' tankards just means getting sloshed - most likely in a medieval setting. However, the phrase could absolutely be a euphemism for something (like getting railed in a sundress by an Hobgoblin, or getting boofed by a Bugbear).
"Avast ye! Hast thou been Clankin' Tankards at the Gasping Gander?? I can see the juices all over yer face!"