Effects of turns on single politician (7)
I believe the answer is:
impacts
'effects' is the definition.
(impact is a kind of effect)
'turns on single politician' is the wordplay.
'turns' becomes 'acts' ('act' can be a synonym of 'turn'**).
'on' says to put letters next to each other.
'single' becomes 'i' (one).
'politician' becomes 'mp'.
'i'+'mp'='imp'
'acts' after 'imp' is 'IMPACTS'.
'of' is the link.
(Other definitions for impacts that I've seen before include "It's camp (anag)" , "Bumps into, collides with" , "Collisions of jolts" .)