Nature walks for dogs (6)
I believe the answer is:
Here is my best explanation:
'dogs' is the definition.
('trail' can be a synonym of 'dog')
I can't explain the remainder of the clue.
(Other definitions for trails that I've seen before include "Paths through, say, a forest", "Follows - footpaths in the wild", "Paths or tracks through wild or hilly country", "Is behind", "Footpaths in the wild", "Lags behind", "Goes after", "Follows or drags behind" and "Tracks, paths".)