Yes, OFFENCE is a Scrabble word!

Letter values in Scrabble US: O 1, F 4, F 4, E 1, N 1, C 3, E 1.

Is it a valid word?

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

the action of attacking an enemy
the team that has the ball (or puck) and is trying to score
a feeling of anger caused by being offended
a lack of politeness; a failure to show regard for others; wounding the feelings or others
(criminal law) an act punishable by law; usually considered an evil act

Also: offensive activity, criminal offense, criminal offence, law-breaking.