Right and left-wingers penning notes (7)
I believe the answer is:
redress
'right' is the definition.
(synonyms)
'left-wingers penning notes' is the wordplay.
'left-wingers' becomes 'reds' (red is a kind of left-winger).
'penning' is an insertion indicator.
'notes' becomes 'res' (I've seen this before).
'reds' going around 'res' is 'REDRESS'.
'and' is the link.
(Other definitions for redress that I've seen before include "Reparation" , "Prepare again - satisfaction" , "remedy" , "Make amends for" , "relief" .)