Crossword Genius

Unexpected flood under the bridge? (9)

Ross

I believe the answer is:

nosebleed

I'm a little stuck... Click here to teach me more about this clue!

'bridge?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for nosebleed that I've seen before include "Outpouring from snout" , "Epistaxis" , "Result of a punch on the schnozzle?" .)

I've seen this clue in The Telegraph.
Want a hint initially instead of a full solution? Install my app