The most common and most likely answer to this crossword clue is the 4 letter word OVID
I've seen this crossword clue in The Times
O
V
I
D
More clues leading to the result OVID
- Some provided source of Latin poetry
- Ancient linesman in short film chasing ball
- Classical writer of film given Oscar at first
- Old poet repulsed male singer
- Poet‘s 40% of Providence
- Old poet’s current disease beginning to disappear
- Poet in old film
- Old tanner?
- Classical author I’d nothing against at first
- Poet separated when half upset
Buddy explains!

The straight part
We know that "Ancient linesman" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ancient linesman = ovid.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.