Backing out of rehearsals is wrong for him (3)
I believe the answer is:
her
'for him' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for her that I've seen before include "The female's" , "Belonging to a female" , "That lady's" , "That lady" , "Pronoun used of ship" .)