Clothing item (6)
(Other definitions for topcoat that I've seen before include "Final layer of paint" , "Ulster?" , "Heavy winter outer garment" , "clothing" , "It's worn on the outside in winter" .)
'clothing item' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for garment that I've seen before include "dress, perhaps" , "coat maybe" , "Covering" , "stole, perhaps" , "Something put on" .)
(Other definitions for sweatshirt that I've seen before include "Long-sleeved, knitted cotton sweater" , "casual gear" , "Long-sleeved top worn by athletes" , "leisurewear" .)
(Other definitions for jacket that I've seen before include "Short hip-length coat" , "Record sleeve" , "Outer garment or casing" , "in which King Edward got very hot" , "See 1" .)
(Another definition for sports jacket that I've seen is " Casual garment".)