Yes, SUPPLICATION is a Scrabble word!

Letter values in Scrabble US: S 1, U 1, P 3, P 3, L 1, I 1, C 3, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

a prayer asking God's help as part of a religious service
a humble request for help from someone in authority
the act of communicating with a deity (especially as a petition or in adoration or contrition or thanksgiving)