Athlete's garment? (6)
I believe the answer is:
jumper
I believe this is a double definition.
'athlete's' is the first definition.
(jumper is a kind of athlete)
'garment?' is the second definition.
(jumper is a kind of garment)
(Other definitions for jumper that I've seen before include "Woollen garment" , "Top" , "Kangaroo and knitted garment" , "Wire to close a circuit" , "Piece of clothing; one leaping" .)