Filming part of theatre where reports may be heard (8,7)
I believe the answer is:
shooting gallery
'where reports may be heard' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'filming part of theatre' is the wordplay.
'filming' becomes 'shooting' ('shoot' can be a synonym of 'film').
'part of theatre' becomes 'gallery' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'shooting'+'gallery'='SHOOTING-GALLERY'
Can you help me to learn more?
(Other definitions for shooting gallery that I've seen before include "Where one may be on target" , "A fair range" , "targets here to aim at?" , "Where one might get high" , "drug-users here" .)