Waterproof jacket (6)
'waterproof jacket' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for anorak that I've seen before include "Jacket for an obsessive?" , "Garment; studious person" , "good on most figures?" , "Raincoat" , "Casual outerwear" .)
(Other definitions for oilskin that I've seen before include "Waterproof garment" , "foul weather item" , "Waterproof fabric" , "Raincoat" , "Heavy-duty waterproof" .)
(Other definitions for cagoule that I've seen before include "Waterproof garment" , "Hooded waterproof anarak" , "coat" , "hooded top" , "Hooded jacket" .)