Praise former lover to all in the centre (5)
I believe the answer is:
'praise' is the definition.
(I know that extol is a more specific form of the action praise)
'former lover to all in the centre' is the wordplay.
'former lover' becomes 'ex' (ex-lover).
'in the centre' indicates the central letters.
The middle letter of 'all' is 'l'.
(Other definitions for extol that I've seen before include "Talk up" , "Acclaim" , "Praise enthusiastically" , "Exalt" , "Crack up" .)