Protesting Republican not doing too well (7)
I believe the answer is:
railing
'protesting' is the definition.
(to rail against something is to protest it)
'republican not doing too well' is the wordplay.
'republican' becomes 'r' (abbreviation).
'not doing too well' becomes 'ailing' (ailing is being unwell).
'r'+'ailing'='RAILING'
(Other definitions for railing that I've seen before include "Noisily protesting" , "Banter" , "Type of fence - scoffing" , "Metal barrier" , "Annoying" .)