hiddencatch
nounUK /ˌhɪdən ˈkætʃ/
US /ˌhɪdən ˈkætʃ/
A hidden catch is a secret problem that you only find out about later.
The free toy seemed great, but the hidden catch was that you had to buy batteries.
OTHER MEANINGS
2. A small hook or clasp that is hard to see.
The necklace closed with a hidden catch at the back.
3. A secret way of holding something shut.
The box had a hidden catch that opened when you pressed the corner.
4. A tricky rule in a game or deal that is not told at first.
The contest had a hidden catch: you had to finish before noon.