The most common and most likely answer to this crossword clue is the 7 letter word COMMAND
I've seen this crossword clue in Financial Times
C
O
M
M
A
N
D
More clues leading to the result COMMAND
- Understanding an order
- Order of butterfly, new discovery initially
- Key, third in bunch and one that opens drawer
- Require company employee to live in Maryland
- Order of fish male servant tucks into
- Bidding millions, fellow admitted to hoax
- Order arms, for example, for the military
- Order, no doubt for starters
- Fellow goes round motorway in what might be battered Fiat
- Understanding group of high-ranking officers
Buddy explains!

The straight part
We know that "Key" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case key = command.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 COMMAND mean?
COMMAND noun- An order to do something.
- The right or authority to order, control or dispose of; the right to be obeyed or to compel obedience.
- Power of control, direction or disposal; mastery.
- A position of chief authority; a position involving the right or power to order or control.
- The act of commanding; exercise or authority of influence.
- A body or troops, or any naval or military force, under the control of a particular officer; by extension, any object or body in someone's charge.
- Dominating situation; range or control or oversight; extent of view or outlook.
- A directive to a computer program acting as an interpreter of some kind, in order to perform a specific task.
- The degree of control a pitcher has over his pitches.
- A command performance.
- To order, give orders; to compel or direct with authority.
- To have or exercise supreme power, control or authority over, especially military; to have under direction or control.
- To require with authority; to demand, order, enjoin.
- To dominate through ability, resources, position etc.; to overlook.
- To exact, compel or secure by influence; to deserve, claim.
- To hold, to control the use of.
- To have a view, as from a superior position.
- To direct to come; to bestow.