Yes, GANGWAYS is a Scrabble word!

Letter values in Scrabble US: G 2, A 1, N 1, G 2, W 4, A 1, Y 4, S 1.

Is it a valid word?

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

a temporary passageway of planks (as over mud on a building site)
a temporary bridge for getting on and off a vessel at dockside
passageway between seating areas as in an auditorium or passenger vehicle or between areas of shelves of goods as in stores

Not playable in Scrabble US: GANGBOARD.