Yes, MOCKERY is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, C 3, K 5, E 1, R 1, Y 4.

Is it a valid word?

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

showing your contempt by derision
a composition that imitates or misrepresents somebody's style, usually in a humorous way
humorous or satirical mimicry

Also: put-on.