Opposed to, in dialect (4)
I believe the answer is:
agin
'opposed to in dialect' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for agin that I've seen before include "Opposed to local" , "Not a fan of" , "Against (facetious)" , "Not in favour of" , "Dialect form of against" .)