Last character elected with Conservative element (4)
I believe the answer is:
zinc
'element' is the definition.
(I know that Zinc is a type of post-transition metal)
'last character elected with conservative' is the wordplay.
'last character' becomes 'Z'.
'elected' becomes 'in' (in government).
'with' says to put letters next to each other.
'conservative' becomes 'C' (UK political abbreviation).
'z'+'in'+'c'='ZINC'
(Other definitions for zinc that I've seen before include "Mineral" , "Blue-white metallic element, atomic number 30" , "Metal, Zn" , "Metal alloyed with copper to make brass" , "Sivery-white metal" .)