The most common and most likely answer to this crossword clue is the 6 letter word VASSAL
I've seen this crossword clue in The Daily Telegraph
V
A
S
S
A
L
More clues leading to the result VASSAL
- Subordinate from Virginia upset girl
- Very stupid person, a learner who must submit to his master?
- Subject of, e.g Leaving Las Vegas, getting drunk
- Land-holder is womankeeping donkey
- Subordinate as slave endlessly mistreated
- I’m treated as slave almost
- Subordinate strand of fever Victor brought back
- Endeavour, perhaps, to get an A for each English subject
- Young woman raised south of Virginia as servant
- Girl with a very withdrawn servant
Buddy explains!

The straight part
We know that "Subordinate" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case subordinate = vassal.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 VASSAL mean?
VASSAL noun- The grantee of a fief, feud, or fee; one who keeps land of a superior, and who vows fidelity and homage to him, normally a lord of a manor; a feudatory; a feudal tenant.
- A subordinate
- To treat as a vassal or to reduce to the position of a vassal; to subject to control; to enslave.
- To subordinate to someone or something.
- Resembling a vassal; slavish; servile.