Yes, CEASING is a Scrabble word!

Letter values in Scrabble US: C 3, E 1, A 1, S 1, I 1, N 1, G 2.

Is it a valid word?

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

put an end to a state or an activity
have an end, in a temporal, spatial, or quantitative sense; either spatial or metaphorical

Also: give up, lay off.