Yes, FUND is a Scrabble word!

Letter values in Scrabble US: F 4, U 1, N 1, D 2.

Is it a valid word?

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

a reserve of money set aside for some purpose
a supply of something available for future use
a financial institution that sells shares to individuals and invests in securities issued by other companies

convert (short-term floating debt) into long-term debt that bears fixed interest and is represented by bonds
place or store up in a fund for accumulation
provide a fund for the redemption of principal or payment of interest
invest money in government securities
accumulate a fund for the discharge of a recurrent liability
furnish money for

Also: monetary fund, investment company, investment trust, investment firm.