Embarrassing Conservative — awful Tory whinger (12)
I believe the answer is:
cringeworthy
'embarrassing' is the definition.
(cringeworthy can mean very embarrassing)
'conservative awful tory whinger' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'awful' indicates anagramming the letters.
'tory'+'whinger'='torywhinger'
'torywhinger' is an anagram of 'ringeworthy'.
'c'+'ringeworthy'='CRINGEWORTHY'
(Other definitions for cringeworthy that I've seen before include "Severely embarrassing" , "Causing embarrassment" , "Acutely embarrassing" .)