Hotel diner finds radiator (6)
I believe the answer is:
heater
'radiator' is the definition.
(I've seen this before)
'hotel diner' is the wordplay.
'hotel' becomes 'h' (phonetic alphabet).
'diner' becomes 'eater' (to dine is to eat a meal).
'h'+'eater'='HEATER'
'finds' is the link.
(Other definitions for heater that I've seen before include "Room warmer" , "Radiator" , "Warming device" , "Source of warmth; gun" , "fire" .)