Yes, LOPPER is a Scrabble word!

Letter values in Scrabble US: L 1, O 1, P 3, P 3, E 1, R 1.

Is it a valid word?

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

a long-handled pruning saw with a curved blade at the end and sometimes a clipper; used to prune small trees

Also: pruning hook.