Idle talk about milliner (7)
I believe the answer is:
chatter
'idle talk' is the definition.
(I've seen this before)
'about milliner' is the wordplay.
'about' becomes 'c' (abbreviation for circa).
'milliner' becomes 'hatter' (synonyms).
'c'+'hatter'='CHATTER'
(Other definitions for chatter that I've seen before include "Rabbit on" , "Talk noisily" , "Babble or gossip" , "Insignificant talk" , "Talk informally" .)