Sullen sorts

MOPERS

Think of those who drag their feet and sigh often, especially when they're stuck in a gloomy mood. You might find them slumped in a corner.

"Sullen sorts" describes people who are gloomy or bad-tempered, which fits "mopers"—those who sulk or move slowly with low energy. The word "mopers" directly ties to the idea of someone being moody or withdrawn, making it a straightforward definition clue. No wordplay or tricks here, just a clear match between the clue’s meaning and the answer.