Yes, INFUSION is a Scrabble word!

Letter values in Scrabble US: I 1, N 1, F 4, U 1, S 1, I 1, O 1, N 1.

Is it a valid word?

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

a solution obtained by steeping or soaking a substance (usually in water)
the process of extracting certain active properties (as a drug from a plant) by steeping or soaking (usually in water)
(medicine) the passive introduction of a substance (a fluid or drug or electrolyte) into a vein or between tissues (as by gravitational force)
the act of infusing or introducing a certain modifying element or quality