Solution

CEILING

2 clues

Overhead surface

Word class: Common noun
Nature of clue: Description
Difficulty: Very easy
Sources: Boatload Puzzles
Topics: Building - Construction - Architecture

Upper limit

Word class: Common noun
Nature of clue: Description
Difficulty: Easy
Sources: Boatload Puzzles
Topics: Numbers - Quantity - Units - Size

Other solutions to Upper limit

Words are categorized by artificial intelligence: there can be mistakes.