Yes, CANVASS is a Scrabble word!

Letter values in Scrabble US: C 3, A 1, N 1, V 4, A 1, S 1, S 1.

Is it a valid word?

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

the setting for a narrative or fictional or dramatic account
an inquiry into public opinion conducted by interviewing a random sample of people
a large piece of fabric (usually canvas fabric) by means of which wind is used to propel a sailing vessel
a tent made of canvas fabric
an oil painting on canvas fabric
the mat that forms the floor of the ring in which boxers or professional wrestlers compete
a heavy, closely woven fabric (used for clothing or chairs or sails or tents)
a heavy, closely woven fabric (used for clothing or chairs or sails or tents)
an oil painting on canvas fabric
the setting for a narrative or fictional or dramatic account
a tent made of canvas fabric
a large piece of fabric (usually canvas fabric) by means of which wind is used to propel a sailing vessel
the mat that forms the floor of the ring in which boxers or professional wrestlers compete

get the opinions (of people) by asking specific questions
solicit votes from potential voters in an electoral campaign
consider in detail and subject to an analysis in order to discover essential features or meaning
solicit votes from potential voters in an electoral campaign
get the opinions (of people) by asking specific questions
cover with canvas
consider in detail and subject to an analysis in order to discover essential features or meaning

Also: opinion poll, public opinion poll, canvas tent.