Yes, SUBVERSION is a Scrabble word!

Letter values in Scrabble US: S 1, U 1, B 3, V 4, E 1, R 1, S 1, I 1, O 1, N 1.

Is it a valid word?

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

destroying someone's (or some group's) honesty or loyalty; undermining moral integrity
the act of subverting; as overthrowing or destroying a legally constituted government

Also: subversive activity.