The most common and most likely answer to this crossword clue is the 10 letter word IMPOVERISH
I've seen this crossword clue in The Times
I
M
P
O
V
E
R
I
S
H
More clues leading to the result IMPOVERISH
- Mischievous about remaining beggar
- Naughty nurses on top of beggar
- Ruin arch, crushing above
- One politician finished his career bankrupt
- Bankrupt making mischief about surplus
- What’s naughty about maiden, maybe being put in reduced circumstances
- Finished being entertained by mischievous beggar
- Goblin, at the end of his meandering, is bankrupt
- Mischievous bears on top of drain
Buddy explains!

The straight part
We know that "beggar" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case beggar = impoverish.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 IMPOVERISH mean?
IMPOVERISH verb- To make poor.
- To weaken in quality; to deprive of some strength or richness.
- To become poor.