Used, as a chair

SATON

Think of the past tense action you’d do to occupy this piece of furniture.

The clue "Used, as a chair" hints at the past tense of "sit," which is "sat." The answer "SATON" adds "on" to "sat" because you sit on a chair, making it a straightforward charade-style clue where the words combine directly. It’s a simple play on the phrase "sat on," which literally describes how a chair is used.