They give up introducing new underwear (8)
I believe the answer is:
knickers
'underwear' is the definition.
(I've seen this before)
'they give up introducing new' is the wordplay.
'they give up' becomes 'kickers' (kick can mean to give up eg to kick drugs).
'introducing' indicates putting letters inside (some letters introduced or inserted into others).
'new' becomes 'n'.
'kickers' enclosing 'n' is 'KNICKERS'.
(Other definitions for knickers that I've seen before include "Underpants" , "Garment (not to be twisted!)" , "Mild expletive" , "Elasticated undergarment" , "Pants" .)