Regard support protecting a chest muscle (7)
I believe the answer is:
respect
'regard' is the definition.
(I know that regard can be written as respect)
'support protecting a chest muscle' is the wordplay.
'support' becomes 'rest' (e.g. a shoulder rest is a support for shoulder).
'protecting' is an insertion indicator (inserted letters are held or protected).
'a chest muscle' becomes 'pec' (pectoral muscle).
'rest' going around 'pec' is 'RESPECT'.
(Other definitions for respect that I've seen before include "Show honour to" , "Admire, think highly of" , "Avoid offending" , "Have high regard for sceptre" , "Refuse to offend" .)