The most common and most likely answer to this crossword clue is the 10 letter word COMPLIANCE
I've seen this crossword clue in The Daily Telegraph
C
O
M
P
L
I
A
N
C
E
Buddy explains!

The straight part
We know that "toeing the line" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case toeing the line = compliance.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 COMPLIANCE mean?
COMPLIANCE noun- An act of complying.
- The state of being compliant.
- The tendency of conforming with or agreeing to the wishes of others.
- A measure of the extension or displacement of a loaded structure; its flexibility
- The accuracy with which a patient follows an agreed treatment plan
- The department of a business that ensures all government regulations are complied with.