Lead Conservative in deeper wickedly (7)
I believe the answer is:
precede
'lead' is the definition.
(synonyms)
'conservative in deeper wickedly' is the wordplay.
'conservative' becomes 'C' (abbreviation commonly used in UK politics).
'in' means one lot of letters goes inside another.
'wickedly' is an anagram indicator.
'deeper' with letters rearranged gives 'preede'.
'c' placed inside 'preede' is 'PRECEDE'.
(Other definitions for precede that I've seen before include "Go before (someone)" , "Go ahead of" , "Come or go before" , "Go in front" , "Antedate" .)