Which sounds the better way to bring in the burgundy trend for fall for warm tone blonde, a velvet clutch with a chain or an infinity scard?

"Warm tone blonde" sounds like you are a Spring, so I sense that the clutch will work better for you. The infinity scarf will work if paired with a warm camel tones near your face. If the scarf is bunched up around your neck it might be too much, unless the infinity scarf is a print or plaid that has other "Spring" compatible colors in it repeating another accent color in your ensemble. In that case you could have both the clutch (solid velvet burgundy) and the multi color (burgundy prominent) infinity scarf.

Or burgundy trousers or skirt might be a way of introducing the colour. - Though you only asked whether a clutch or a scarf. :)