Dope enjoyed consuming bit of roast (4)
I believe the answer is:
drug
'dope' is the definition.
(thesaurus)
'enjoyed consuming bit of roast' is the wordplay.
'enjoyed' becomes 'dug' (slang).
'consuming' indicates putting letters inside.
'bit of' indicates taking the first letters.
The first letter of 'roast' is 'r'.
'dug' going around 'r' is 'DRUG'.
(Other definitions for drug that I've seen before include "Pharmaceutical (or recreational) item" , "Chemical medicament" , "Medical or narcotic substance" , "may be soft or hard" , "LSD, say" .)