Yes, FIXATIVE is a Scrabble word!

Letter values in Scrabble US: F 4, I 1, X 8, A 1, T 1, I 1, V 4, E 1.

Is it a valid word?

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

a compound (such as ethanol or formaldehyde) that fixes tissues and cells for microscopic study
a varnish dissolved in alcohol and sprayed over pictures to prevent smudging