Female leaving old seafood (5)
I believe the answer is:
ormer
'seafood' is the definition.
(I've seen this before)
'female leaving old' is the wordplay.
'female' becomes 'f' (common abbreviation).
'leaving' suggests deleting specific letters.
'old' becomes 'former' (eg a former president, an old president).
'former' with 'f' taken out is 'ORMER'.
(Other definitions for ormer that I've seen before include "Mollusc" , "Ear-shaped shell" , "Shellfish" , "sea creature" , "Seafood" .)