We let actors supply loo (5,6)
I believe the answer is:
water closet
'loo' is the definition.
('water closet' can be a synonym of 'loo')
'we let actors supply' is the wordplay.
'supply' indicates anagramming the letters (supply of letters to make).
'we'+'let'+'actors'='weletactors'
'weletactors' is an anagram of 'WATER-CLOSET'.
(Other definitions for water closet that I've seen before include "John" , "A cow's letter (anag) - WC" , "Sanitary convenience" , "Lavatory" , "WC in full" .)