Republican, with help from others, made comeback (7)
I believe the answer is:
rallied
'made comeback' is the definition.
(rally can mean to recover or make a comeback)
'republican with help from others' is the wordplay.
'republican' becomes 'R' (abbreviation in US politics).
'with help from others' becomes 'allied' (allied with other people).
'r'+'allied'='RALLIED'
(Other definitions for rallied that I've seen before include "(Of shares) increased in value after a fall" , "Recovered in health" , "Brought together" , "Recovered strength after illness, or entered driving competition" , "Gathered" .)