Yes, DEFLATE is a Scrabble word!

Letter values in Scrabble US: D 2, E 1, F 4, L 1, A 1, T 1, E 1.

Is it a valid word?

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

collapse by releasing contained air or gas
release contained air or gas from
reduce or lessen the size or importance of
produce deflation in
reduce or cut back the amount or availability of, creating a decline in value or prices
become deflated or flaccid, as by losing air