Yes, ARRANGEMENT is a Scrabble word!

Letter values in Scrabble US: A 1, R 1, R 1, A 1, N 1, G 2, E 1, M 3, E 1, N 1, T 1.

Is it a valid word?

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

the thing arranged or agreed to
an orderly grouping (of things or persons) considered as a unit; the result of arranging
an organized structure for arranging or classifying
the spatial property of the way in which something is placed
a piece of music that has been adapted for performance by a particular set of voices or instruments
the act of arranging and adapting a piece of music

Also: musical arrangement.