Not harsh with him (7)
I believe the answer is:
clement
'him' is the definition.
'not harsh' is the wordplay.
I cannot really understand how this works, but
'not' could be 'nt' (synonyms) and 'nt' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'with' is the link.
Can you help me to learn more?
(Other definitions for clement that I've seen before include "nice" , "Several popes" , "Kindly (applied to weather)" , "Merciful, lenient" , "opponent for Winston" .)