light beer vs lager beer

light beer and lager beer both are nouns.

Word	Noun	Adjective	Verb	Adverb
light beer	Yes	No	No	No
lager beer	Yes	No	No	No

As nouns, lager beer is a hypernym of light beer; that is, lager beer is a word with a broader meaning than light beer:

light beer: lager with reduced alcohol content
lager beer: a general term for beer made with bottom fermenting yeast (usually by decoction mashing); originally it was brewed in March or April and matured until September

Other hypernyms of light beer include lager.

light beer (noun)	lager beer (noun)
lager with reduced alcohol content	a general term for beer made with bottom fermenting yeast (usually by decoction mashing); originally it was brewed in March or April and matured until September