Insect, bird and fish (9)
I believe the answer is:
cockroach
'insect' is the definition.
(cockroach is a kind of insect)
'bird and fish' is the wordplay.
'bird' becomes 'cock' (cock is a kind of bird).
'and' means one lot of letters go next to another.
'fish' becomes 'roach' (roach is a kind of fish).
'cock'+'roach'='COCKROACH'
(Other definitions for cockroach that I've seen before include "Rock coach turns out to be an insect" , "So-called black beetle" , "Household insect pest" , "Cork coach can be a pest" , "Beetle-like insect" .)