Jacket takes sheen off case hardening, perhaps (8)
I believe the answer is:
cardigan
'jacket' is the definition.
(I've seen this before)
'sheen off case hardening perhaps' is the wordplay.
'off' indicates named letters should be taken away.
'perhaps' indicates anagramming the letters.
'case'+'hardening'='casehardening'
'casehardening' with 'sheen' taken out is 'caarding'.
'caarding' with letters rearranged gives 'CARDIGAN'.
'takes' acts as a link.
(Other definitions for cardigan that I've seen before include "Welsh town; garment" , "in wardrobe?" , "Woollen jacket" , "part of Wales once" , "Woollen garment" .)