Possibly `ilong^i garment (6)
I believe the answer is:
jumper
'garment' is the definition.
(jumper is a kind of garment)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for jumper that I've seen before include "Wire to close a circuit" , "Sweater" , "Horse, athlete and knitted garment" , "Knitwear - bounder" , "Kangaroo and knitted garment" .)