Praise former lover returning fortune (5)
I believe the answer is:
extol
'praise' is the definition.
(extolling is a kind of praising)
'former lover returning fortune' is the wordplay.
'former lover' becomes 'ex'.
'returning' says the letters should be written backwards.
'fortune' becomes 'lot' ('lot' can be a synonym of 'fortune').
'lot' reversed gives 'tol'.
'ex'+'tol'='EXTOL'
(Other definitions for extol that I've seen before include "be lavish with praise" , "trumpet" , "Talk up" , "Praise with enthusiasm" , "Crack up" .)