The most common and most likely answer to this crossword clue is the 8 letter word SEMIOTIC
I've seen this crossword clue in The Sunday Telegraph
S
E
M
I
O
T
I
C
More clues leading to the result SEMIOTIC
Buddy explains!

The straight part
We know that "Concerned with signs" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case concerned with signs = semiotic.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.
What does SEMIOTIC mean?
SEMIOTIC adjective- Of or relating to semiotics or to semantics.
- Of or relating to the signs or symptoms of diseases.