Something afoot for a fellow with grit (6)
I believe the answer is:
sandal
'something afoot' is the definition.
(whimsically, something worn on a foot)
'a fellow with grit' is the wordplay.
'a fellow' becomes 'al' (I've seen this in other clues).
'with' is a charade indicator (letters next to each other).
'grit' becomes 'sa nd' (synonyms).
'al' put after 'sand' is 'SANDAL'.
'for' acts as a link.
(Other definitions for sandal that I've seen before include "An open shoe for summer" , "Light open shoe" , "Wood" , "Light footwear" , "Light strapped shoe" .)