What is a 'clutch' in competitive gaming? (Not in the car sense)
The term "clutch" was originally used in sports commentary, describing a player that can keep their head cool and perform well during a tense moment in a game, where the outcome of the competition was at stake.
Definitions of "clutch" (adjective):
happening during a very important or critical time especially in a sports competition
able to perform well in a very important or critical situation especially in a sports competition
This term has since migrated to competitive gaming, where is used in similar situations, usually in professional gaming events where there is a lot at stake.
A good example of the term is used in a recent IGN article on the International Dota 2 Championships:
Alliance and Na'Vi. Competitive Dota 2 fans dreams came true when the grand finals came down to an incredibly clutch play in the last match of the best of five series.
In FPS games such as Counter-Strike or Call of Duty, I've always heard the term used with a slightly different meaning.
If everyone on your team dies and you are now alone against multiple enemies, and you win the round, we'd say it "was a clutch" or you "clutched".
In this context, it means you won the round against all odds. It doesn't necessarily mean the round was critical or game-changing.
It means how well you perform under pressure, for example in the crucial moment of the game when it is decided who wins and looses. So Flygon would be a good Pokémon to have in such situations.