No reason to start blaze (7)
I believe the answer is:
inferno
'blaze' is the definition.
(I've seen this before)
'no reason to start' is the wordplay.
'reason' becomes 'infer' (both can mean to deduce).
'to start' means one lot of letters go next to another.
'no' after 'infer' is 'INFERNO'.
(Other definitions for inferno that I've seen before include "Furious" , "Big fire" , "Nine Circles here" , "A raging fire like hell" , "A raging fire as in hell - ask Dante" .)