Talk up erstwhile turn of fate (5)
I believe the answer is:
extol
'talk up' is the definition.
(I've seen this before)
'erstwhile turn of fate' is the wordplay.
'erstwhile' becomes 'ex'.
'turn of' shows that the letters should be reversed in order (I've seen 'turn' mean this).
'fate' becomes 'lot' ('lot' can be a synonym of 'fate').
'lot' back-to-front is 'tol'.
'ex'+'tol'='EXTOL'
(Other definitions for extol that I've seen before include "Sing the praises of" , "celebrate" , "Laud; glorify" , "Praise - honour" , "Highly rate" .)