Charge to take back Big Bird outfit (7)
I believe the answer is:
costume
'outfit' is the definition.
(I've seen this before)
'charge to take back big bird' is the wordplay.
'charge' becomes 'cost' (I've seen this in other clues).
'to take' says to put letters next to each other.
'back' shows that the letters should be reversed in order.
'big bird' becomes 'emu' (type of large bird).
'emu' reversed gives 'ume'.
'cost'+'ume'='COSTUME'
(Other definitions for costume that I've seen before include "(Historic etc) dress" , "Actor's attire" , "Clothes for a play or fancy dress ball" , "Actor's set of clothes" , "Duds" .)