Dogs are, we hear, wearing formal evening attire (6)
I believe the answer is:
trails
'dogs' is the definition.
('trail' can be a synonym of 'dog')
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for trails that I've seen before include "Follows - footpaths in the wild" , "Paths or tracks through wild or hilly country" , "Follows or drags behind" , "Goes after" , "Paths through, say, a forest" .)