After study I will have fireplace to blacken (9)
I believe the answer is:
denigrate
'to blacken' is the definition.
(thesaurus)
'after study i will have' is the wordplay.
'after' is a charade indicator (letters next to each other).
'study' becomes 'den' (I've seen this before).
'will have' becomes 'grate' (I can't explain this - if you can you should give a lot more credence to this answer).
'den' next to 'i' is 'deni'.
'deni'+'grate'='DENIGRATE'
'fireplace' acts as a link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for denigrate that I've seen before include "Slight" , "Run down" , "Bad-mouth" , "Disparage" , "Criticise, belittle" .)