Conservative with update for guiding principles (5)
I believe the answer is:
credo
'guiding principles' is the definition.
(I've seen this before)
'conservative with update' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'with' is a charade indicator (letters next to each other).
'update' becomes 're-do' (I've seen this in another clue).
'c'+'redo'='CREDO'
'for' is the link.
(Other definitions for credo that I've seen before include "Statement of faith" , "Set of beliefs about leftist circle" , "Part of the Latin Mass" , "System of principles" , "Mass movement" .)