Modifying, changing (8)
I believe the answer is:
altering
This clue is a double definition.
'modifying' is the first definition.
(thesaurus)
'changing' is the second definition.
(altering is a kind of changing)
(Other definitions for altering that I've seen before include "Making changes" , "Changing -- 1 across (anag)" , "revising" , "Modifying, changing" , "making a change" .)