Doctrinal belief (5)
I believe the answer is:
tenet
'doctrinal belief' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tenet that I've seen before include "That's the law" , "Adiaphoron" , "Conviction" , "Dogma or principle" , "A belief or credo - it's a palindrome" .)