Dope mostly found in Stone shot full of barbiturates (7)
I believe the answer is:
sedated
'shot full of barbiturates' is the definition.
(barbiturates are a type of sedative)
'dope mostly found in stone' is the wordplay.
'dope' becomes 'data' (dope can informally mean information).
'mostly' means to remove the last letter.
'found in' indicates putting letters inside.
'stone' becomes 'seed' (eg the stone from a fruit).
'data' with its last letter taken away is 'dat'.
'dat' put inside 'seed' is 'SEDATED'.
(Other definitions for sedated that I've seen before include "Tranquillized" , "Given a tranquilliser" , "Calmed with drugs" , "Dead set (anag) - tranquillised" , "kept calm" .)