Depends on the fabric. Is it real cloth tweed, or the fake tweed looking tolex stuff, like on many newer guitar amps? With real tweed, I've done relicing with a 50/50 mix of Bulleye Amber shellac, then clear coated with Minwax Wipe On Poly, for a nice old weathered tweed look. It seals the tweed well against dirt & water. Actually, I also did that on a tweed Peavey guitar amp, with the faux tweed tolex covering. If no aging/darkening is needed, you could just seal it with the Wipe On Poly, or the rattlecan spray version, which comes in gloss or satin. I prefer satin, and get better control with the wipe on version, using a rag or small brush. If you use that, just be sure to let it dry well before putting uke in the case, so the poly smell doesn't get into your uke.