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' indicates anagramming the letters (another form of the letters).
'bizarre' anagrammed gives 'BRAZIER'.
'of' acts as a 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" .)