… as Goldberg and sheep celebrate raucously (5,2,2)

'celebrate raucously' is the definition.
(to whoop it up is to party or celebrate)

'as goldberg and sheep' is the wordplay.
I cannot really see how this works, but
'goldberg' could be 'whoopi' (actress Whoopi Goldberg) and 'whoopi' is present in the answer.
'sheep' could be 'tup' (tup is a kind of sheep) and 'tup' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).