Yes, BARRIER is a Scrabble word!

Letter values in Scrabble US: B 3, A 1, R 1, R 1, I 1, E 1, R 1.

Is it a valid word?

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

a structure or object that impedes free movement
any condition that makes it difficult to make progress or to achieve an objective
anything serving to maintain separation by obstructing vision or access