expression, noun
snack or dish served with alcohol; drinking accompaniment
Refers to food eaten while drinking, ranging from simple snacks to elaborate dishes. The phrase is a set expression; 肴 is read さかな and means 'side dish for drinks'.
酒の肴に枝豆を頼んだ。
I ordered edamame as a snack with my drink.
この店は酒の肴が豊富で、日本酒が進む。
This place has a great variety of drinking snacks, which makes the sake go down well.
A more casual, everyday term for snacks eaten with alcohol. 酒の肴 is slightly more traditional or literary.
The standalone noun 肴 can also mean 'appetizer for drinks', but 酒の肴 is a fixed phrase emphasizing the drinking context.
Compound of 酒 (sake, 'alcohol') + の (possessive particle) + 肴 (sakana, 'side dish for drinks'). The reading さかな for 肴 is an old specialized meaning distinct from the more common 魚 (sakana, 'fish').