Item of footwear that's a hit (4)
I believe the answer is:
sock
This clue is a double definition.
'item of footwear' is the first definition.
(I've seen this before)
'that's a hit' is the second definition.
(I've seen this in another clue)
(Other definitions for sock that I've seen before include "One worn" , "impact" , "one with wind" , "component of Christmas present" , "Foot covering" .)