Cryptic crossword clue
, 18 Labour hope Corbyn, a red, is excellent 6,8

The most common and most likely answer to this crossword clue is the 6 plus 8 letter word BEYOND REPROACH

I've seen this crossword clue in The Guardian
B
E
Y
O
N
D
R
E
P
R
O
A
C
H

Buddy explains!

The straight part
We know that "excellent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case excellent = beyond reproach.
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.

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