"A clout" is an item of apparel (4)
I believe the answer is:
sock
This clue is a triple definition!
'a clout' is the first definition.
(I've seen this in another clue)
'is' acts as a link.
'an item' is the second definition.
(I have seen 'Item of clothing' mean 'sock' so perhaps 'item' could also mean 'sock')
'of' acts as a link.
'apparel' is the third definition.
(sock is a kind of apparel)
(Other definitions for sock that I've seen before include "one with wind" , "One worn" , "One going into Oxford maybe" , "Foot-covering" , "Article to cover extremity" .)