Cod is cooked a bit as musical entertainment (5)
I believe the answer is:
disco
'musical entertainment' is the definition.
(I've seen this before)
'cod is cooked a bit' is the wordplay.
'a bit' indicates the answer is hidden within the clue (the answer is formed by a bit of the clue).
'DISCO' can be found hidden inside 'cod is cooked'.
'as' acts as a link.
(Other definitions for disco that I've seen before include "Thumping music" , "Modern dancehall of youth" , "equipment for playing recordings" , "Party with records" , "Club or party with dancing" .)