Admire muscle in repose (7)
I believe the answer is:
respect
'admire' is the definition.
(admire can mean to respect)
'muscle in repose' is the wordplay.
'muscle' becomes 'pec' (I've seen this in other clues).
'in' is an insertion indicator.
'repose' becomes 'rest' (synonyms).
'pec' inserted into 'rest' is 'RESPECT'.
(Other definitions for respect that I've seen before include "Venerate" , "Regard and treat well" , "Pay attention to" , "Observe" , "Appreciate - courtesy" .)