The most common and most likely answer to this crossword clue is the 2 plus 1 plus 7 letter word TO A SKYLARK
I've seen this crossword clue in The Times
T
O
A
S
K
Y
L
A
R
K
More clues leading to the result TO A SKYLARK
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 = to a skylark.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.