The most common and most likely answer to this crossword clue is the 3 plus 2 letter word RUN ON
I've seen this crossword clue in The Times
R
U
N
O
N
Buddy explains!
The straight part
We know that "Keep racing/continue in the same line" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case keep racing/continue in the same line = run on.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 RUN ON mean?
RUN ON noun- (etc.) An amount of time spent playing on the field during a game, especially so as to evaluate a player's abilities.
- A run-on sentence.
- Anything that runs on, such as a run-on entry in a dictionary.
- The period when a power saw or other tool continues to run after being powered off.
- Continuing on where a rhetorical pause would be more appropriate.
- Placed or coming at the end of something, such as at the end of a dictionary entry.