Slow on the uptake

DENSE

Thick-headed might describe both a stubborn person and this five-letter word.

"Slow on the uptake" is a phrase that describes someone who takes a while to understand things, often implying they’re not very quick-witted. The answer "DENSE" fits because it can mean both physically compact (like a thick material) and, in slang, slow to grasp ideas—like a person who’s a bit thickheaded. The clue plays on the double meaning of "dense," using the idea of being slow to connect it to the informal sense of the word. It’s a straightforward definition with a hint of wordplay in how "dense" bridges literal and figurative meanings.