Send back theatre subsidy - it stops waste (6)
I believe the answer is:
diaper
'it stops waste' is the definition.
The definition suggests a singular noun which matches the answer.
'send back theatre subsidy' is the wordplay.
'send back' shows that the letters should be reversed in order.
'theatre' becomes 'rep' (repertory theatre).
'subsidy' becomes 'aid' (I've seen this in another clue).
'rep'+'aid'='repaid'
'repaid' in reverse letter order is 'DIAPER'.
Can you help me to learn more?
(Other definitions for diaper that I've seen before include "type of paving" , "An American nappy" , "Baby's nappy" .)