A swimming exhibition? (8)
I believe the answer is:
aquarium
'a swimming exhibition?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
This is the entire clue.
Can you help me to learn more?
(Other definitions for aquarium that I've seen before include "Large fish tank" , "Tank for aquatic life" , "Fish tank or maring museum" , "A kind of fish zoo" , "Glass tank for fish" .)