Yes, DROPPER is a Scrabble word!

Letter values in Scrabble US: D 2, R 1, O 1, P 3, P 3, E 1, R 1.

Is it a valid word?

DROPPER is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

pipet consisting of a small tube with a vacuum bulb at one end for drawing liquid in and releasing it a drop at a time

Also: eye dropper.