Spike takes honey off Greyhound (4)
I believe the answer is:
drug
'spike' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for drug that I've seen before include "Medicinal substance" , "Chemical used for medical reasons" , "may be soft or hard" , "Perhaps grass" , "Pharmaceutical (or recreational) item" .)