Co-operative stores such an entertaining experience (5)
I believe the answer is:
opera
'entertaining experience' is the definition.
'co-operative stores such an' is the wordplay.
I cannot really see how this works, but
'an' could be 'per' (synonymous as in 'once an hour', 'once per hour') and 'per' is located in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for opera that I've seen before include "works in Latin" , "The Magic Flute, say" , "some theatrics" , "Macbeth, perhaps" , "Musical extravaganza" .)