Mean to alter handle (4)
I believe the answer is:
name
'handle' is the definition.
(handle can mean a name or nickname)
'mean to alter' is the wordplay.
'to alter' indicates an anagram.
'mean' with letters rearranged gives 'NAME'.
(Other definitions for name that I've seen before include "Reputation; identify" , "By which a person is known" , "Amen (anag)" , "Baptise" , "Title; famous person" .)