cup of tea vs activity

cup of tea and activity both are nouns.

Word	Noun	Adjective	Verb	Adverb
cup of tea	Yes	No	No	No
activity	Yes	No	No	No

As nouns, activity is a hypernym of cup of tea; that is, activity is a word with a broader meaning than cup of tea:

cup of tea (noun)	activity (noun)
an activity that you like or at which you are superior	any specific behavior
	the trait of being active; moving or acting rapidly and energetically
	an organic process that takes place in the body
	a process existing in or produced by nature (rather than by the intent of human beings)
	the state of being active
	(chemistry) the capacity of a substance to take part in a chemical reaction