Clot of a drug doctor going round Megastore (8)
I believe the answer is:
embolism
'clot' is the definition.
(I have seen 'obstructive clot' mean 'embolism' so perhaps 'clot' could also mean 'embolism')
'drug doctor going round megastore' is the wordplay.
I cannot quite understand how this works, but
'drug' could be 'e' (E is another name for ecstasy) and 'e' is found in the answer.
'doctor' could be 'mb' (Bachelor of Medicine, Medicinae Baccalaureus) and 'mb' is found in the answer.
'round' could be 'o' (round can mean a round object) and 'o' is found within the answer.
This explanation may well be incorrect...
'of a' acts as a link.
Can you help me to learn more?
(Other definitions for embolism that I've seen before include "obstructive clot" , "Blood vessel blockage" , "Blockage of an artery" , "Arterial obstruction" , "Obstruction of artery by blood clot" .)