No longer going to church, having left to thrive (5)
I believe the answer is:
excel
'thrive' is the definition.
Although both the answer and definition are verbs in their base form, I cannot see how they can define each other.
'no longer going to church having left' is the wordplay.
'no longer' becomes 'ex' (prefix meaning former or onetime).
'going to' is a charade indicator (letters next to each other).
'church' becomes 'ce' (abbreviation for Church of England).
'having' is a charade indicator (letters next to each other).
'left' becomes 'l' (common abbreviation).
'ex'+'ce'+'l'='EXCEL'
'to' is the link.
Can you help me to learn more?
(Other definitions for excel that I've seen before include "Outrival" , "Do superbly well" , "Perform outstandingly well" , "Be the best" , "Do particularly well" .)