Yes, FLANKERS is a Scrabble word!

Letter values in Scrabble US: F 4, L 1, A 1, N 1, K 5, E 1, R 1, S 1.

Is it a valid word?

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

a back stationed wide of the scrimmage line; used as a pass receiver
a soldier who is a member of a detachment assigned to guard the flanks of a military formation

Also: flanker back.