Number facing Leftist regularly sacrificed principles (6)
I believe the answer is:
tenets
'principles' is the definition.
(I've seen this in another clue)
'number facing leftist regularly sacrificed' is the wordplay.
'number' becomes 'ten' (ten is a kind of number).
'facing' is a charade indicator (letters next to each other).
'regularly sacrificed' means one should take alternating letters (letters removed at regular intervals).
The alternating letters of 'leftist' are 'ets'.
'ten'+'ets'='TENETS'
(Other definitions for tenets that I've seen before include "Doctrines of belief" , "Conviction" , "gnomes?" , "We stand by these" , "Principles, doctrines" .)