Yes, HEADLOCK is a Scrabble word!

Letter values in Scrabble US: H 4, E 1, A 1, D 2, L 1, O 1, C 3, K 5.

Is it a valid word?

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

a wrestling hold in which the opponent's head is locked between the crook of your elbow and the side of your body