Deduce knight stuck in raging fire (5)
I believe the answer is:
infer
'deduce' is the definition.
(synonyms)
'knight stuck in raging fire' is the wordplay.
'knight' becomes 'n' (chess).
'stuck in' means one lot of letters goes inside another.
'raging' indicates anagramming the letters.
'fire' anagrammed gives 'ifer'.
'n' put within 'ifer' is 'INFER'.
(Other definitions for infer that I've seen before include "Deduce, surmise" , "Establish by deduction" , "'Deduce, conclude (5)'" , "Conjecture" , "come to a conclusion" .)