Praise luck turning on former partner (5)
I believe the answer is:
extol
'praise' is the definition.
(extolling is a kind of praising)
'luck turning on former partner' is the wordplay.
'luck' becomes 'lot' ('lot' can be a synonym of 'luck').
'turning' shows that the letters should be reversed in order.
'on' is a charade indicator (letters next to each other).
'former partner' becomes 'ex'.
'lot' reversed gives 'tol'.
'tol' put after 'ex' is 'EXTOL'.
(Other definitions for extol that I've seen before include "Say great things about" , "Highly rate" , "Highly commend" , "Praise with enthusiasm" , "be lavish with praise" .)