Bird left home to get fish? (6)
I believe the answer is:
linnet
'bird' is the definition.
(linnet is a kind of bird)
'left home to get fish?' is the wordplay.
'left' becomes 'l' (common abbreviation).
'home' becomes 'in' ('he's home' can mean 'he's in').
'to get' says to put letters next to each other.
'fish?' becomes 'net' (netting fish is a kind of fishing**).
'l'+'in'+'net'='LINNET'
(Other definitions for linnet that I've seen before include "See three down" , "Winger" , "A British finch" , "Songbird in Lent" , "House finch" .)