Fabulous bird takes hour to eat a fish (5)
I believe the answer is:
roach
'fish' is the definition.
(roach is a kind of fish)
'fabulous bird takes hour to eat a' is the wordplay.
'fabulous bird' becomes 'roc' (I've seen this before).
'takes' is a charade indicator (letters next to each other).
'hour' becomes 'h'.
'to eat' is an insertion indicator.
'roc'+'h'='roch'
'roch' enclosing 'a' is 'ROACH'.
(Other definitions for roach that I've seen before include "Freshwatwer fish" , "Historic SE county" , "bedbug in the Waldorf?" , "Trim" , "Maybe catch" .)