Brothel where nothing, in idle chat, is given up (6)
I believe the answer is:
bagnio
'brothel' is the definition.
(synonyms)
'nothing in idle chat is given up' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'idle chat' becomes 'gab' (gab can mean chat or talk).
'is given up' says the letters should be written in reverse (in a down clue, letters go up).
'o'+'in'+'gab'='oingab'
'oingab' written backwards gives 'BAGNIO'.
'where' acts as a link.
(Other definitions for bagnio that I've seen before include "disorderly house" , "Bordello" .)