A struggle to maintain faith (4,3)
I believe the answer is:
'faith' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?
'a struggle to maintain' is the wordplay.
'a struggle' becomes 'war' (I've seen this in another clue).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'maintain' becomes 'holy' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'war' put after 'holy' is 'HOLY WAR'.
Can you help me to learn more?
(Other definitions for holy war that I've seen before include "Jihad" , "Religious conflict" .)