Bouncer starts to regret awfully big brawl in tavern (6)
I believe the answer is:
rabbit
'bouncer' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'starts to regret awfully big brawl in tavern' is the wordplay.
'starts to' indicates taking the first letters.
The initial letters of 'regret awfully big brawl in tavern' is 'RABBIT'.
Can you help me to learn more?
(Other definitions for rabbit that I've seen before include "Bunny; chatter idly" , "Game" , "Yak" , "family pet?" , "Burrowing mammal" .)