Harsh as I've to restrain supporter (8)
I believe the answer is:
abrasive
'harsh' is the definition.
(I've seen this before)
'as i've to restrain supporter' is the wordplay.
'to restrain' indicates putting letters inside.
'supporter' becomes 'bra' (a bra gives support to breasts).
'as'+'ive'='asive'
'asive' enclosing 'bra' is 'ABRASIVE'.
(Other definitions for abrasive that I've seen before include "Grinding substance" , "Harsh, causing angry feelings" , "Causing irritation" , "Rough, as sandpaper" , "Tending to grind down" .)