Cry out in pain (4)
I believe the answer is:
yelp
'cry out in pain' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for yelp that I've seen before include "Little dog's bark" , "Squeal" , "Barking" , "Short sharp cry (of such as a dog)" , "Short sharp cry or bark" .)