Conservative perhaps lying over the European disaster (7)
I believe the answer is:
debacle
'disaster' is the definition.
(synonyms)
'conservative perhaps lying over the european' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'perhaps lying' becomes 'abed' (lying abed).
'over' is a reversal indicator.
'the european' becomes 'le'.
'c'+'abed'='cabed'
'cabed' back-to-front is 'debac'.
'debac'+'le'='DEBACLE'
(Other definitions for debacle that I've seen before include "Sudden and ignominious failure" , "Fiasco, a right mess" , "Sudden and violent collapse" , "Total disorder or defeat" , "Disatrous collapse" .)