tennis lesson vs lesson

tennis lesson and lesson both are nouns.

Word	Noun	Adjective	Verb	Adverb
tennis lesson	Yes	No	No	No
lesson	Yes	No	No	No

As nouns, lesson is a hypernym of tennis lesson; that is, lesson is a word with a broader meaning than tennis lesson:

tennis lesson (noun)	lesson (noun)
a lesson in playing tennis	a task assigned for individual study
	a unit of instruction
	punishment intended as a warning to others
	the significance of a story or event