Nazareth icehouse partly illustrates principle (5)
I believe the answer is:
ethic
'principle' is the definition.
(ethic is a kind of principle)
'nazareth icehouse partly' is the wordplay.
'partly' indicates a hidden word (part of the clue is used).
'ETHIC' is hidden in the letters of 'nazareth icehouse'.
'illustrates' is the link.
(Other definitions for ethic that I've seen before include "Moral value" , "Set of moral values" , "System of principles" , "An unusual factor in morals" , "Principles accepted by a social group" .)