It may be burnt — that's blooming insane! (6)
I believe the answer is:
sienna
'it may be burnt' is the definition.
(I've seen this in another clue)
'blooming insane' is the wordplay.
'blooming' indicates an anagram (I've seen this in other clues).
'insane' with letters rearranged gives 'SIENNA'.
'that's' acts as a link.
(Other definitions for sienna that I've seen before include "Brownish-yellow colour" , "Yellow-brown clay used in paint pigments" , "Yellow-brown pigment" , "A shade" , "Pigment obtained from earth" .)