Yes, PLEDGING is a Scrabble word!

Letter values in Scrabble US: P 3, L 1, E 1, D 2, G 2, I 1, N 1, G 2.

Is it a valid word?

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

promise solemnly and formally
pay (an amount of money) as a contribution to a charity or service, especially at regular intervals
propose a toast to
give as a guarantee
bind or secure by a pledge