Considerately treat muscle during inactivity (7)
I believe the answer is:
respect
'considerately treat' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'muscle during inactivity' is the wordplay.
'muscle' becomes 'pec' (pectoral muscle).
'during' indicates putting letters inside.
'inactivity' becomes 'rest' (rest is a kind of inactivity).
'pec' placed inside 'rest' is 'RESPECT'.
Can you help me to learn more?
(Other definitions for respect that I've seen before include "Pay attention to" , "Have high regard for sceptre" , "value" , "Point" , "Reverence" .)