They pinch children (7)
I believe the answer is:
'children' is the definition.
('nipper' can be a synonym of 'child')
'they pinch' is the wordplay.
I cannot quite see how this works, but
'pinch' could be 'nip' (nip can mean to pinch or bite) and 'nip' is found within the answer.
The remaining letters 'pers' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nippers that I've seen before include "Small children" , "They put the squeeze on" , "Claws; children" , "pickpockets" , "kids?" .)