A bird if fearful's not caught (5)
I believe the answer is:
raven
'a bird' is the definition.
(raven is a kind of bird)
'fearful's not caught' is the wordplay.
'fearful' becomes 'craven' ('craven' can be a synonym of 'fearful').
'not' suggests deleting specific letters.
'caught' becomes 'c' (cricket abbreviation).
'craven' with 'c' taken away is 'RAVEN'.
'if' is the link.
(Other definitions for raven that I've seen before include "Hungrily devour" , "Large blue-black bird" , "Black crow" , "Bird of ill omen" , "Large bird of the crow family" .)