The most common and most likely answer to this crossword clue is the 3 plus 6 plus 8 letter word SIR ROBERT CHILTERN
I've seen this crossword clue in The Guardian
S
I
R
R
O
B
E
R
T
C
H
I
L
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E
R
N
Buddy explains!
The straight part
We know that "26 character /26 character" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case 26 character /26 character = sir robert chiltern.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.