Yes, SUPPRESSION is a Scrabble word!

Letter values in Scrabble US: S 1, U 1, P 3, P 3, R 1, E 1, S 1, S 1, I 1, O 1, N 1.

Is it a valid word?

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

the failure to develop some part or organ
the act of withholding or withdrawing some book or writing from publication or circulation
forceful prevention; putting down by power or authority
(psychology) the conscious exclusion of unacceptable thoughts or desires