An agreement perhaps is pure counter — play on words, if not unsatisfactory (6)
I believe the answer is:
prenup
'an agreement perhaps is pure counter play' is the definition.
I know nothing about this answer so I can't judge whether this works.
'on words if not unsatisfactory' is the wordplay.
I cannot quite see how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for prenup that I've seen before include "Agreement drawn up before the wedding" , "Contract before marriage, in short" , "Legal agreement before marriage" , "Contract between those about to marry" , "Financial agreement in case of divorce made by a couple before marriage (abbr)" .)