Opposing move, one reckons (7)
I believe the answer is:
counter
'opposing' is the definition.
(I've seen this before)
'move one reckons' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'un' (northern English dialect form of 'one') and 'un' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for counter that I've seen before include "Piece in board game" , "It's quite the opposite" , "Contrary" , "Parry" , "Game piece; oppose" .)