Dior has always made quality mascara as part of their Diorshow line . Dior Diorshow Iconic Mascara is a particularly impressive one. It was created for fashion shows and red carpet events, and gives incredible length. It also defines the lashes well, and adds a bit a curl. I had no clumping issues with it.
For best results with this one (and with any mascara for that matter) curl your lashes, wipe the brush first and apply one light coat. Wait for the first coat to dry and apply a second coat.
Diorshow Iconic will last all day and is quite smudge and smear proof.