Novel way to betray high-class furniture maker (8)
I believe the answer is:
sheraton
'high-class furniture maker' is the definition.
(18th-century furniture designer Thomas Sheraton)
'novel way to betray' is the wordplay.
'novel' becomes 'she' (I've seen this before).
'way to betray' becomes 'rat on' (to rat on someone is to betray them).
'she'+'raton'='SHERATON'
(Other definitions for sheraton that I've seen before include "Thomas -, English furniture-maker" , "Style of English furniture found in North Sea" , "Another's (anag) - style of furniture" , "He produced furniture" , "Eng. furniture designer" .)