Wait for a fish to be born first (4)
I believe the answer is:
bide
'wait for' is the definition.
'a fish to be born first' is the wordplay.
'a fish' becomes 'ide' (I've seen this before**).
'to be born' becomes 'b'.
'first' says to put letters next to each other.
'ide' put after 'b' is 'BIDE'.
(Other definitions for bide that I've seen before include "Dwell, stay" , "Remain or stay (poetically)" , "Stay (obs.)" , "Remain (archaic)" , "Tarry" .)