The most common and most likely answer to this crossword clue is the 4 letter word OBEY
I've seen this crossword clue in The Daily Telegraph
O
B
E
Y
More clues leading to the result OBEY
- Follow old Turkish governor
- Conform to orders, being extra yielding at first
- Follow orders of former pupil, easy as flying off
- Do as told and honour Yankee
- Carry out gong followed by Yankee
- Follow youth leader after gong for service
- Comply with order unknown
- Follow the introduction of Ottoman governor
- Carry out gong before end of ceremony
- Follow order how to address Turkish governor?
Buddy explains!

The straight part
We know that "toe the line" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case toe the line = obey.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 OBEY mean?
OBEY verb- To do as ordered by (a person, institution etc), to act according to the bidding of.
- To do as one is told.
- To be obedient, compliant (to a given law, restriction etc.).