Wall of Sand's description reads as follows (emphasis mine):
You conjure up a wall of swirling sand on the ground at a point you can see within range. You can make the wall up to 30 feet long, 10 feet high, and 10 feet thick, and it vanishes when the spell ends. It blocks line of sight but not movement. A creature is blinded while in the wall’s space and must spend 3 feet of movement for every 1 foot it moves there.
To me, it's unclear whether or not the bolded clause provides total cover to a creature behind the wall, or if the creature is simply heavily obscured. If you and another creature are on the opposite sides of a Wall of Sand, can you perform a ranged weapon or spell attack against the creature?
Best Answer
Yes, you can attack through a Wall of Sand.
"Obstacle" is not a game term, but all the examples given are of solid objects (walls, trees, creatures, and furniture), which agrees with the dictionary definition "a thing that blocks one's way" (Lexico).
As you've noted, Wall of Sand does not block movement, so it is not an obstacle, and therefore does not provide total cover.
As a side note, the attack would have disadvantage, since
except that the target can't see you either (assuming it doesn't have blindsight or similar abilities), and
so the advantage and disadvantage would cancel out.