Muscle work out is clear (7)
I believe the answer is:
absolve
'is clear' is the definition.
(thesaurus)
'muscle work out' is the wordplay.
'muscle' becomes 'ab' (short for abdominal muscle).
'work out' becomes 'solve' (I've seen this before).
'ab'+'solve'='ABSOLVE'
(Other definitions for absolve that I've seen before include "Excuse" , "Clear of blame or guilt" , "Free (a person) from guilt" , "Grant remission of a sin" , "Lob vase (anag.)" .)