Ability to engage with Northern church (10)
I believe the answer is:
competence
'ability' is the definition.
(I know that competence is a type of ability)
'engage with northern church' is the wordplay.
'engage with' becomes 'compete' (I can't explain this - if you can you should give a lot more credence to this answer).
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'church' becomes 'CE' (abbreviation for Church of England).
'compete'+'n'+'ce'='COMPETENCE'
'to' is the link.
Can you help me to learn more?
(Other definitions for competence that I've seen before include "Fitness, suitability" , "authority" , "skill" , "Efficiency; legal power" , "State of ability" .)