The most common and most likely answer to this crossword clue is the 7 letter word ECHELON
I've seen this crossword clue in The Guardian
E
C
H
E
L
O
N
More clues leading to the result ECHELON
- Group he left to engage in economics
- Rank slipping on leech!
- Rank scent, obscene and frightful, essentially. Musk, perhaps
- False clone claiming ambassador’s rank
- Morning gone, chameleon switches position
- Musk used by eastern church is rank
- Part of the creche longs for rank
- Level of assistance mostly found in European prisoner
- The man’s into clone reproduction in classHEin anagramof CLONE
- Feedback about deal regularly reaches new level
Buddy explains!

The straight part
We know that "rank" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rank = echelon.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 ECHELON mean?
ECHELON noun- A level or rank in an organization, profession, or society.
- A line of riders seeking maximum drafting in a crosswind, resulting in a diagonal line across the road.
- A formation of troops, ships, etc., in diagonal parallel rows.
- To form troops into an echelon.
- Of a matrix: having undergone Gaussian elimination with the result that the leading coefficient or pivot (that is, the first nonzero number from the left) of a nonzero row is to the right of the pivot of the row above it, giving rise to a stepped appearance in the matrix.