Cryptic crossword clue
Weird slogan by US feller using old language 5-5

The most common and most likely answer to this crossword clue is the 11 letter word ANGLO-SAXON

I've seen this crossword clue in Financial Times
A
N
G
L
O
-
S
A
X
O
N

Buddy explains!

The straight part
We know that "old language" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old language = anglo-saxon.
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.

Crossword Answer definitions

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