Money enclosures (6)
I believe the answer is:
pounds
'money enclosures' is the definition.
'pounds' can be an answer for 'enclosures' (pound is a kind of enclosure). I am not sure about the 'money' bit.
'money enclosures' is the wordplay.
'money' becomes 'pound' (pound sterling).
'enclosures' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'pound'+'s'='POUNDS'
(Other definitions for pounds that I've seen before include "Strikes; money" , "Enclosures for dogs and cars" , "Imperial units of weight" , "Crushes or beats with repeated blows" , "Sterling units or imperial weights" .)