One politician is a scoundrel (3)
I believe the answer is:
imp
'a scoundrel' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'one politician' is the wordplay.
'one' becomes 'i' (Roman numeral).
'politician' becomes 'MP' (Member of Parliament).
'i'+'mp'='IMP'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for imp that I've seen before include "A small mischievous devil" , "little chap" , "Little mischief-maker" , "A mischievous little devil" , "puck" .)