Yes, ALLEGORY is a Scrabble word!

Letter values in Scrabble US: A 1, L 1, L 1, E 1, G 2, O 1, R 1, Y 4.

Is it a valid word?

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

a short moral story (often with animal characters)
a visible symbol representing an abstract idea
an expressive style that uses fictional characters and events to describe some subject by suggestive resemblances; an extended metaphor