Digressions (8)
I believe the answer is:
tangents
'digressions' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tangents that I've seen before include "Straight lines that touch but don't intersect a curve" , "Straight lines that touche curves" , "Straight lines - ten gnats (anag)" , "Touching lines" , "Straight lines that touch curves" .)