Right, go on – backslide! (7)
I believe the answer is:
relapse
'backslide' is the definition.
(I've seen this before)
'right go on' is the wordplay.
'right' becomes 'r' (common abbreviation).
'go on' becomes 'elapse' (elapsing is a kind of going on).
'r'+'elapse'='RELAPSE'
(Other definitions for relapse that I've seen before include "A return to illness" , "Take a turn for the worse" , "Medical setback" , "unfortunate medical state" , "Fall back into former state" .)