Guiding doctrine (5)
I believe the answer is:
tenet
'guiding doctrine' 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 "Matter of belief" , "A palindromic doctrine or creed" , "Palindromic principle or belief" , "Article of belief" , "Belief or doctrine - a palindrome" .)