It is a verb that means "to be accustomed to/be in the habit of".
I would say that is a little odd phrasing in English. It may have been said like that previously or maybe still in some dialects, but I am not overly sure.
'Use' being used to mean a habitual action or being accustomed to something tends only to appear as 'used': whether as a past tense verb ('I used to walk to school') or a past participle ('I am used to walking to school').
"Use to" almost always appears in the past tense, "used to [dance]...", and means something a little different: it indicates a customary or regular past action (and often implies it isn't happening now), and so the Latin imperfect ("saltabat") would be a better translation of it than "saltare solet".