What will have treatment in store? (6,7)
I believe the answer is:
retail therapy
'store?' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?
'what will have treatment' is the wordplay.
I cannot really understand how this works, but
'treatment' could be 'therapy' ('therapy' can be a synonym of 'treatment') and 'therapy' is found within the answer.
The remaining letters 'retail' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'in' is the link.
(Other definitions for retail therapy that I've seen before include "Shopping, facetiously" , "spending for treatment?" .)