Bird left Noah's ship (4)
I believe the answer is:
lark
'bird' is the definition.
(lark is a kind of bird)
'left noah's ship' is the wordplay.
'left' becomes 'l' (common abbreviation).
'noah's ship' becomes 'ark' (Noah's ark in the Bible).
'l'+'ark'='LARK'
(Other definitions for lark that I've seen before include "Bird that sings on the wing" , "Amusing adventure; bird" , "Harmless adventure" , "Rise with this bird to get up early" , "Bird - caper" .)