Chemist at inquest concealing a drug (6)
I believe the answer is:
statin
'a drug' is the definition.
(type of drug)
'chemist at inquest concealing' is the wordplay.
'concealing' indicates a hidden word.
'STATIN' can be found hidden inside 'chemist at inquest'.
(Other definitions for statin that I've seen before include "Cholesterol-lowering drug" , "Drug given to reduce blood cholesterol" , "Drug reducing cholesterol" , "Cholesterol-reducing drug" .)