Very active Conservative splitting left (7)
I believe the answer is:
excited
'very' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?
'active conservative splitting left' is the wordplay.
'active conservative' becomes 'c' (abbreviation commonly used in UK politics. I am not sure about the 'active' bit.).
'splitting' indicates putting letters inside.
'left' becomes 'exited' ('exit' can be a synonym of 'leave').
'c' inserted into 'exited' is 'EXCITED'.
(Other definitions for excited that I've seen before include "Aroused; eager" , "moved by emotion" , "in a state of agitation" , "Aroused, enthused" , "Roused by strong emotion" .)