Do this to physique to make exercise valueless (6)
I believe the answer is:
hollow
'valueless' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for hollow that I've seen before include "Dent; echoey" , "Concave; empty inside" , "Empty - insincere" , "Empty space within" , "Having a cavity inside" .)