The most common and most likely answer to this crossword clue is the 4 plus 4 plus 4 letter word AULD LANG SYNE
I've seen this crossword clue in The Guardian
A
U
L
D
L
A
N
G
S
Y
N
E
More clues leading to the result AULD LANG SYNE
- Analysed lung, damaged many years ago
- Song rendered by lea lady, sung badly
- US and England lay in ruins in days of yore
- Traditional chorus in England, say, rendered around middle of July
- and 19a: Cast laud Spooner’s chanted lyric in topical song
- Not usually England‘s lay, rendered about the middle of January
- Slay England, struggling around the beginning of union in the distant past
- The Good Old Days’, for which we will take a cup in singing
- Ugandans yell about traditional song
- 16a & 21d Ugandans yell out words in friendly celebration
Buddy explains!
The straight part
We know that "days of yore" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case days of yore = auld lang syne.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.