Woollen garments? New kit surprisingly upset the Gunners! (8)
I believe the answer is:
knitwear
'woollen garments?' is the definition.
(I've seen this before)
'new kit surprisingly upset the gunners' is the wordplay.
'surprisingly' is an anagram indicator.
'upset' is a reversal indicator.
'the gunners' becomes 'ra' (Royal Artillery).
'ra' backwards is 'ar'.
'new'+'kit'='newkit'
'newkit' with letters rearranged gives 'knitwe'.
'knitwe'+'ar'='KNITWEAR'
(Other definitions for knitwear that I've seen before include "Woollen items" , "Woollen clothing" , "such as often goes over shirts and blouses" , "stockings, perhaps" , "Woollen clothes" .)