Search out sin, confused, burning (10)
I believe the answer is:
combustion
'burning' is the definition.
(I know that burning can be written as combustion)
'search out sin confused' is the wordplay.
'search' becomes 'comb' (combing is a kind of searching).
'confused' indicates anagramming the letters.
'out'+'sin'='outsin'
'outsin' anagrammed gives 'ustion'.
'comb'+'ustion'='COMBUSTION'
(Other definitions for combustion that I've seen before include "Process of burning" , "See 12 and 20" .)