The most common and most likely answer to this crossword clue is the 6 letter word MOTTOS
I've seen this crossword clue in The Daily Telegraph
M
O
T
T
O
S
Buddy explains!

The straight part
We know that "slogans" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case slogans = mottos.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 MOTTOS mean?
MOTTOS noun- A sentence, phrase, or word, forming part of an heraldic achievement.
- A sentence, phrase, or word, prefixed to an essay, discourse, chapter, canto, or the like, suggestive of its subject matter; a short, suggestive expression of a guiding principle; a maxim.
- A paper packet containing a sweetmeat, cracker, etc., together with a scrap of paper bearing a motto.