Priest rejecting expression of doubt about core of his religion (5)
I believe the answer is:
faith
'religion' is the definition.
(synonyms)
'priest rejecting expression of doubt about core of his' is the wordplay.
I cannot quite see how this works, but
'about' could be 'a' (abbreviation in Chambers) and 'a' is found within the answer.
'expression' could be 'fit' (fit is a kind of expression) and 'fit' is found within the leftover letters.
A single letter 'h' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for faith that I've seen before include "Unshakeable belief" , "Religious belief" , "A woman" , "Confidence" , "Staunch trust" .)