Pretentious political group losing face (4)
I believe the answer is:
arty
'pretentious' is the definition.
(similar in meaning)
'political group losing face' is the wordplay.
'political group' becomes 'party' (a political party).
'losing face' means to remove the first letter.
'party' with its first letter removed is 'ARTY'.
(Other definitions for arty that I've seen before include "Affectedly unconventional" , "Pretentious, affected" , "Affectedly artistic" , "Affectedly highbrow" , "Affectedly cultural" .)