Yes, CITRON is a Scrabble word!

Letter values in Scrabble US: C 3, I 1, T 1, R 1, O 1, N 1.

Is it a valid word?

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

large lemonlike fruit with thick aromatic rind; usually preserved
thorny evergreen small tree or shrub of India widely cultivated for its large lemonlike fruits that have thick warty rind

Also: citron tree, citrus medica.