Ecstasy found in room backed dishonest talk about heroin trader (8)
I believe the answer is:
merchant
'heroin trader' is the definition.
'merchant' can be an answer for 'trader' (I've seen this before). I'm not sure about the 'heroin' bit.
'ecstasy found in room backed dishonest talk' is the wordplay.
'ecstasy' becomes 'E' (informal term for the drug).
'found in' indicates putting letters inside.
'room' becomes 'rm' (abbreviation for room).
'backed' says the letters should be written in reverse.
'dishonest talk' becomes 'chant' (I can't justify this - if you can you should give a lot more credence to this answer).
'e' placed into 'rm' is 'rem'.
'rem' backwards is 'mer'.
'mer'+'chant'='MERCHANT'
'about' is the link.
(Other definitions for merchant that I've seen before include "Wholesale trader" , "Retail trader" , "Dealer" , "Broker" , "that's often associated with speed" .)