The most common and most likely answer to this crossword clue is the 7 letter word ODYSSEY
I've seen this crossword clue in The Guardian
O
D
Y
S
S
E
Y
More clues leading to the result ODYSSEY
- Headless corpse is sent back for certain journey
- Poem about Ulysses centrally with ugly conclusion?
- Headless corpse’s certainly set back long journey
- Part of somebody’s Seychelles journey
- Poem about Ulysses essentially reaching journey’s end
- A classic, right? Sun’s back chasing topless figure
- A long wandering tale
- Poem about Ulysses essentially at end of Troy
- Goodbyes as sexy regularly producing such a journey
- Person’s heading off? Yes, northwards, making long journey
Buddy explains!

The straight part
We know that "A classic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a classic = odyssey.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 ODYSSEY mean?
ODYSSEY noun- An extended adventurous voyage.
- An intellectual or spiritual quest.