Opposing (4)
'opposing' is the definition.
(resisting is a kind of opposing)
This is all the clue.
(Other definitions for resisting that I've seen before include "smart, that!" , "Refraining from" , "Withstanding" .)
'opposing' is the definition.
(prefix meaning 'opposing')
This is the entire clue.
(Other definitions for anti that I've seen before include "on the other side" , "Someone opposed (to a policy?)" , "not favoured" , "[NO MAN]" , "Naysayer" .)