Spinning led to detective twisting muscle (7)
I believe the answer is:
deltoid
'muscle' is the definition.
(deltoid is a kind of muscle)
'spinning led to detective twisting' is the wordplay.
'spinning' is a reversal indicator.
'detective' becomes 'di' (Detective Inspector abbreviation).
'twisting' is a reversal indicator (letters twist back).
'led' backwards is 'del'.
'di' back-to-front is 'id'.
'del'+'to'+'id'='DELTOID'
(Other definitions for deltoid that I've seen before include "Triangular shoulder muscle - old diet (anag)" , "Large triangular muscle that covers shoulder and raises arm" .)