Chap removed from act by necessity (8)
I believe the answer is:
perforce
'by necessity' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for perforce that I've seen before include "Of necessity" , "willy-nilly" , "Necessarily, arising from free crop" , "Unavoidably" , "without choice" .)