The most common and most likely answer to this crossword clue is the 8 letter word TRACKAGE
I've seen this crossword clue in The Guardian
T
R
A
C
K
A
G
E
Buddy explains!
The straight part
We know that "lines" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lines = trackage.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TRACKAGE mean?
TRACKAGE noun- Railway tracks collectively
- The right of a railway company to use the tracks belonging to another; the charge levied for this right
- The act of tracking, or towing, as a boat; towage.