Hear first nocturnal predator cry (4)
I believe the answer is:
howl
'cry' is the definition.
(to howl is to cry out)
'hear first nocturnal predator' is the wordplay.
'hear first' becomes 'h' (1st letter of 'hear').
'nocturnal predator' becomes 'owl' (I've seen this in another clue).
'h'+'owl'='HOWL'
(Other definitions for howl that I've seen before include "Bay, clamour" , "Long wailing cry" , "Cry (with rage or laughter)" , "Wolf sound" , "Screech" .)