The garlic could make you sleepy (9)
I believe the answer is:
lethargic
'sleepy' is the definition.
(thesaurus)
'the garlic could make you' is the wordplay.
'could make you' is an anagram indicator.
'the'+'garlic'='thegarlic'
'thegarlic' with letters rearranged gives 'LETHARGIC'.
(Other definitions for lethargic that I've seen before include "Lacking in energy or vitality" , "Lacking energy/enthusiasm" , "Apathetic, lacking energy" , "lack of energy" , "Unenergetic" .)