Barrier to entry, perhaps

STILE

Think of a simple wooden structure that lets people pass over a fence but might slow down livestock or keep them contained.

"Barrier to entry" hints at something that blocks access, like a gate or fence. The word "perhaps" suggests it might not be a literal barrier—here, it’s a stile, a small structure with steps or bars that lets people climb over fences while keeping livestock in. The clue plays on "entry" both as physical access and the idea of a threshold, making "stile" a clever fit. It’s a common crossword answer for rural or farming-related obstacles.