My first thought was that it's a typo for "unrhyw ffordd", meaning "any road" or "any way". But then I tried googling it. Was the song you found it in a Welsh translation of the "Let it go" from "Frozen" (that was the only hit I got on Google)? There I found the line: "Doedd yr oer byth yn drafferth i mi unrhywyffordd" as a translation of: "The cold never bothered me anyway", so I suppose it means "anyway", but it's the first time I've come across it. It looks to me like an anglicism, based on the English "anyway" (rather than "more Welsh" forms such as "beth bynnag" or "ta beth"). It may be a local dialect form, as it doesn't seem to be widely used.