Elected Conservative is capping yellow tooth (7)
I believe the answer is:
incisor
'tooth' is the definition.
(incisor is a kind of tooth)
'elected conservative is capping yellow' is the wordplay.
'elected' becomes 'in' (in government).
'conservative' becomes 'C' (UK political abbreviation).
'capping yellow' becomes 'or' (I am not sure about this - if you are sure you should believe this answer much more).
'in'+'c'+'is'+'or'='INCISOR'
Can you help me to learn more?
(Other definitions for incisor that I've seen before include "Ivory perhaps" , "One takes a bite" , "carnivore requires?" , "Chisel-edged tooth" , "Canine" .)