Bizarre form of heater (7)
I believe the answer is:
brazier
'heater' is the definition.
(brazier is a kind of heater)
'bizarre form' is the wordplay.
'form' is an anagram indicator (another form of the letters).
'bizarre' with letters rearranged gives 'BRAZIER'.
'of' is the link.
(Other definitions for brazier that I've seen before include "Portable stand for coals" , "Portable coal fire" , "Bizarre (anag)" , "Outdoor burner" , "Portable container for hot coals" .)