Affectedly genteel (2-2-2)
I believe the answer is:
la-di-da
'affectedly genteel' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for la-di-da that I've seen before include "Stuck-up" , "Affectedly genteel" , "Pretentious, snobbish" , "Informally, having affected manner of pronunciation" , "Hoity-toity" .)