Expression of disapproval about desire is, in other words, middle class (11)
I believe the answer is:
bourgeoisie
'middle class' is the definition.
('bourgeoisie' can be a synonym of 'middle class')
'expression of disapproval about desire is in other words' is the subsidiary indication.
'expression of disapproval' becomes 'boo' (I've seen this before).
'about' indicates putting letters inside.
'desire' becomes 'urge' (I've seen this in other clues**).
'in other words' becomes 'ie'.
'boo' placed around 'urge' is 'bourgeo'.
'bourgeo'+'is'+'ie'='bourgeoisie'
(Other definitions for bourgeoisie that I've seen before include "conventional group" , "Middle classes" , "The middle class" .)