African tea vs stimulant drug

African tea and stimulant drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
African tea	Yes	No	No	No
stimulant drug	Yes	No	No	No

As nouns, stimulant drug is a hypernym of African tea; that is, stimulant drug is a word with a broader meaning than African tea:

African tea: the leaves of the shrub Catha edulis which are chewed like tobacco or used to make tea; has the effect of a euphoric stimulant
stimulant drug: a drug that temporarily quickens some vital process

Other hypernyms of African tea include excitant, stimulant.

African tea (noun)	stimulant drug (noun)
the leaves of the shrub Catha edulis which are chewed like tobacco or used to make tea; has the effect of a euphoric stimulant	a drug that temporarily quickens some vital process