This is the 12881st most frequent Russian word.
левой
"Левой" means "left" (directional or related to the left side).
Here, 'левой' is used colloquially to mean 'shady' or 'illicit', indicating an unclear or suspicious nature of the scheme.
Это кажется какой-то левой схемой.
This seems like some shady scheme.
Here, 'левой' is an adjective in the instrumental case agreeing with 'рука', denoting 'left' as opposed to 'right'.
Я держу книгу в левой руке.
I am holding the book in my left hand.
In this sentence, 'левой' describes 'дорога', indicating which specific road, namely the one on the left side.