Yes, ENLARGED is a Scrabble word!

Letter values in Scrabble US: E 1, N 1, L 1, A 1, R 1, G 2, E 1, D 2.

Is it a valid word?

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

make larger
make large
become larger or bigger
add details, as to an account or idea; clarify the meaning of and discourse in a learned way, usually in writing

(of an organ or body part) excessively enlarged as a result of increased size in the constituent cells
as of a photograph; made larger
larger than normal
enlarged to an abnormal degree

Also: blow up, flesh out, blown-up.