Mobilises right supporters (7)
I believe the answer is:
rallies
'mobilises' is the definition.
('rally' can be a synonym of 'mobilize')
'right supporters' is the wordplay.
'right' becomes 'r' (common abbreviation).
'supporters' becomes 'allies' (I've seen this before).
'r'+'allies'='RALLIES'
(Other definitions for rallies that I've seen before include "court exchanges?" , "Extended exchanges of tennis strokes" , "Gets better" , "Mobilizes" , "series of strokes" .)