The most common and most likely answer to this crossword clue is the 3 plus 3 letter word SEE YOU
I've seen this crossword clue in Financial Times
S
E
E
Y
O
U
More clues leading to the result SEE YOU
- Copper reported cheers
- Christian Union on the radio so long
- Cheers poker challenge?
- Vale on borders of Cymru, reportedly?
- Failing eyes, old, start to utter farewell
- Extremists in Cymru heard for so long
- Cheers copper audibly
- Copper shouted farewell
- Audibly spelt out copper’s parting statement
- Copper symbolically said farewell
Buddy explains!
The straight part
We know that "so long" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case so long = see you.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.