Some taco ingredients turned out to make them incredibly drowsy (8)
I believe the answer is:
comatose
'drowsy' is the definition.
(thesaurus)
'some taco ingredients' is the wordplay.
'ingredients' indicates anagramming the letters.
'some'+'taco'='sometaco'
'sometaco' anagrammed gives 'COMATOSE'.
'turned out to make them incredibly' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for comatose that I've seen before include "Deeply unconscious" , "Fast asleep" , "Somnolent" , "Very drowsy, perhaps unconscious" , "Sandman called" .)