Lust after Conservative party (5)
I believe the answer is:
crave
'lust after' is the definition.
(I've seen this before)
'conservative party' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'party' becomes 'rave' (type of dance party).
'c'+'rave'='CRAVE'
(Other definitions for crave that I've seen before include "Feel a powerful desire for (something)" , "Yearn for (something)" , "need, desperately" , "Desire strongly" , "Fairly sizeable" .)