Item of footwear (4)
'item of footwear' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for shoe that I've seen before include "Playing card box" , "Work as a farrier" , "eg Trainer" , "Perhaps casual" , "9 maybe" .)
(Other definitions for sock that I've seen before include "Hit hard; woollen item" , "Hit hard - footwear" , "Strike, hose" , "Thump" , "Foot-covering" .)
(Other definitions for boot that I've seen before include "Dismiss" , "eg Wellington" , "Hard kick (colloq.)" , "Kick; start (a computer)" , "Car luggage space; kick" .)