Yes, INTERFERE is a Scrabble word!

Letter values in Scrabble US: I 1, N 1, T 1, E 1, R 1, F 4, E 1, R 1, E 1.

Is it a valid word?

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

come between so as to be hindrance or obstacle
get involved, so as to alter or hinder an action, or through force or threat of force

Also: step in.