The most common and most likely answer to this crossword clue is the 6 letter word UNIONS
I've seen this crossword clue in Financial Times
U
N
I
O
N
S
More clues leading to the result UNIONS
Buddy explains!
The straight part
We know that "Alliances" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case alliances = unions.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 UNIONS mean?
UNIONS noun- The act of uniting or joining two or more things into one.
- The state of being united or joined; a state of unity or harmony.
- That which is united, or made one; something formed by a combination or coalition of parts or members; a confederation; a consolidated body; a league.
- A trade union; a workers' union.
- An association of students at a university for social and/or political purposes; also in some cases a debating body.
- A joint or other connection uniting parts of machinery, such as pipes.
- The set containing all of the elements of two or more sets.
- The act or state of marriage.
- Sexual intercourse.
- A data structure that can store any of various types of item, but only one at a time.
- A large, high-quality pearl.
- An affiliation of several parishes for joint support and management of their poor; also the jointly-owned workhouse.
- To combine sets using the union operation.