Get back on with success (6)
I believe the answer is:
recoup
'get back' is the definition.
(I've seen this before)
'on with success' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'with' means one lot of letters go next to another.
'success' becomes 'coup' (I've seen this before).
're'+'coup'='RECOUP'
(Other definitions for recoup that I've seen before include "Get back, say expenses" , "Recover, losses perhaps" , "Get back (outlay)" , "Regain a loss through subsequent profits" , "Recover - retrieve" .)