Yes, HUSTLING is a Scrabble word!

Letter values in Scrabble US: H 4, U 1, S 1, T 1, L 1, I 1, N 1, G 2.

Is it a valid word?

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

cause to move furtively and hurriedly
move or cause to move energetically or busily
sell something to or obtain something from by energetic and especially underhanded activity
get by trying hard
pressure or urge someone into an action

Also: bustle about.