premise: A brown squirrel sitting on a branch with an acorn during the fall. hypothesis: Squirrel having a snack.
entailment: Squirrels are known for eating acorns.  A squirrel that has an acorn is likely eating it or will soon be eating it.  Eating a piece of food is often referred to as a snack, so the squirrel is eating the acorn as a snack.