Yes, CITRUS is a Scrabble word!

Letter values in Scrabble US: C 3, I 1, T 1, R 1, U 1, S 1.

Is it a valid word?

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

any of numerous fruits of the genus Citrus having thick rind and juicy pulp; grown in warm regions
any of numerous tropical usually thorny evergreen trees of the genus Citrus having leathery evergreen leaves and widely cultivated for their juicy edible fruits having leathery aromatic rinds

Also: citrus fruit, citrous fruit, citrus tree.