Yes, SPLITTER is a Scrabble word!

Letter values in Scrabble US: S 1, P 3, L 1, I 1, T 1, T 1, E 1, R 1.

Is it a valid word?

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

a worker who splits fish and removes the backbone
a taxonomist who classifies organisms into many groups on the basis of relatively minor characteristics
a laborer who splits logs to build split-rail fences

Also: rail-splitter.