Yes, SHELTER is a Scrabble word!

Letter values in Scrabble US: S 1, H 4, E 1, L 1, T 1, E 1, R 1.

Is it a valid word?

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

a structure that provides privacy and protection from danger
protective covering that provides protection from the weather
the condition of being protected
a way of organizing business to reduce the taxes it must pay on current earnings
temporary housing for homeless or displaced persons

Also: tax shelter.