walnut liqueur vs liqueur

walnut liqueur and liqueur both are nouns.

Word	Noun	Adjective	Verb	Adverb
walnut liqueur	Yes	No	No	No
liqueur	Yes	No	No	No

As nouns, liqueur is a hypernym of walnut liqueur; that is, liqueur is a word with a broader meaning than walnut liqueur:

walnut liqueur: any of a variety of strong alcoholic drinks made of walnuts.
liqueur: strong highly flavored sweet liquor usually drunk after a meal

Other hypernyms of walnut liqueur include cordial.

walnut liqueur (noun)	liqueur (noun)
any of a variety of strong alcoholic drinks made of walnuts.	strong highly flavored sweet liquor usually drunk after a meal