The most common and most likely answer to this crossword clue is the 7 letter word REGENTS
I've seen this crossword clue in The Guardian
R
E
G
E
N
T
S
More clues leading to the result REGENTS
Buddy explains!
The straight part
We know that "They’re temporarily on throne" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they’re temporarily on throne = regents.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 REGENTS mean?
REGENTS 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