Place of convenience, some say (4)
I believe the answer is:
lieu
'place of' is the definition.
(I've seen this before)
'convenience some say' is the wordplay.
'convenience' becomes 'loo' (both can mean a toilet).
'some say' shows a homophone (sound like).
'loo' sounds like 'LIEU'.
(Other definitions for lieu that I've seen before include "'In ..., instead (4)'" , "Stead - place" , "In ... of; in exchange for" , "In - of means instead of" , "The substitute" .)