Yes, TURNOVER is a Scrabble word!

Letter values in Scrabble US: T 1, U 1, R 1, N 1, O 1, V 4, E 1, R 1.

Is it a valid word?

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

the ratio of the number of workers that had to be replaced in a given time period to the average number of workers
a dish made by folding a piece of pastry over a filling
the volume measured in dollars
the act of upsetting something

Also: employee turnover, turnover rate, dollar volume.