Moving supply so parts miles off (7)
I believe the answer is:
lissome
'moving supply' is the definition.
(moving in a supple way)
'so parts miles off' is the wordplay.
'parts' indicates putting letters inside (in the sense of cuts or separates).
'off' indicates anagramming the letters.
'miles' with letters rearranged gives 'lisme'.
'so' inserted inside 'lisme' is 'LISSOME'.
(Other definitions for lissome that I've seen before include "Oil mess (anag)" , "Slim, supple, graceful" , "So smile, being agile and lithe" , "Thin - supple - graceful" , "Willowy" .)