The most common and most likely answer to this crossword clue is the 6 letter word REGENT
I've seen this crossword clue in The Daily Telegraph
R
E
G
E
N
T
More clues leading to the result REGENT
- Temporary ruler, for example, in charge of landlord?
- One ruling for now: note the convenience, in short
- Referring to man, monarch’s stand-in
- King, say, starts to exhibit neurotic tendencies? I may act for him
- Extremely rude chap, one with interim authority
- Extremely responsible chap, one standing in for monarch
- Man succeeding retired queen as interim ruler
- Split involving George – gutless as he was – in 1815
- Fellow to come on scene after monarch’s suffered setback?
- Ruler, for example, fills the breach
Buddy explains!

The straight part
We know that "Queen possibly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case queen possibly = regent.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 REGENT mean?
REGENT noun- A ruler.
- One who rules in place of the monarch, especially because the monarch is too young, absent, or disabled.
- A member of a municipal or civic body of governors, especially in certain European cities.
- A member of governing board of a college or university; also a governor of the Smithsonian Institute in Washington DC.
- The chief executive of a regency
- Ruling; governing; regnant.
- Exercising vicarious authority.