Yes, RETREAT is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, T 1, R 1, E 1, A 1, T 1.

Is it a valid word?

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

(military) withdrawal of troops to a more favorable position to escape the enemy's superior forces or after a defeat
a place of privacy; a place affording peace and quiet
(military) a signal to begin a withdrawal from a dangerous position
(military) a bugle call signaling the lowering of the flag at sunset
an area where you can be alone
withdrawal for prayer and study and meditation
the act of withdrawing or going backward (especially to escape something hazardous or unpleasant)

Also: pull away, draw back, pull back, move back, back out, back away, crawfish out, pull in one's horns.