Give one politician mastery! (6)
I believe the answer is:
impart
'give' is the definition.
(I know that give is a more specific form of evince)
'one politician mastery' is the wordplay.
'one' becomes 'i' (Roman numeral).
'politician' becomes 'MP' (Member of Parliament).
'mastery' becomes 'art' (I've seen this in another clue).
'i'+'mp'+'art'='IMPART'
(Other definitions for impart that I've seen before include "Pass on information" , "Pass on (knowledge, info)" , "Convey information, make known" , "Share, pass on" , "Reveal, make information known" .)