Split Conservative and Labour? (5)
I believe the answer is:
cleft
'split' is the definition.
(I've seen this before)
'conservative and labour?' is the wordplay.
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'and' says to put letters next to each other.
'labour?' becomes 'left' (I've seen this in other clues).
'c'+'left'='CLEFT'
(Other definitions for cleft that I've seen before include "division" , "chasm" , "split along natural lines" , "Narrow opening" , "Split or indentation" .)