Perform Cosi Fan Tutte, perhaps at half-term (7)
I believe the answer is:
operate
'perform' is the definition.
(I've seen this before)
'cosi fan tutte perhaps at half-term' is the wordplay.
'cosi fan tutte perhaps' becomes 'opera' (Cosi Fan Tutte is an example).
'at' means one lot of letters go next to another.
'half-term' becomes 'te'.
'opera'+'te'='OPERATE'
(Other definitions for operate that I've seen before include "Cut - run" , "Work as a surgeon" , "Control, run, a mcahine say" , "Cause to function" , "Function; run" .)