From 素(す) (su-) + 揚(あ)げ (age, “連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 揚(あ)げる (ageru).”).
素(す)揚(あ)げ • (suage) ←すあげ (suage)?