Yes, ARROWROOT is a Scrabble word!

Letter values in Scrabble US: A 1, R 1, R 1, O 1, W 4, R 1, O 1, O 1, T 1.

Is it a valid word?

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

a nutritive starch obtained from the root of the arrowroot plant
white-flowered West Indian plant whose root yields arrowroot starch
canna grown especially for its edible rootstock from which arrowroot starch is obtained

Also: american arrowroot, obedience plant, maranta arundinaceae, indian shot, canna indica, canna edulis.

Not playable in Scrabble US: ACHIRA.