Two tunnels under a bridge? (8)
I believe the answer is:
nostrils
'two tunnels' is the definition.
Although both the answer and definition are plural nouns, I can't see how one could define the other.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for nostrils that I've seen before include "Slit Ron's nose parts" , "Nose-openings" , "Holes in noses" , "Openings in the nose" , "Openings to the nasal cavity" .)