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 can't justify this - if you can 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" .)