The most common and most likely answer to this crossword clue is the 10 letter word UNATTENDED
U
N
A
T
T
E
N
D
E
D
More clues leading to the result UNATTENDED
Buddy explains!

The straight part
We know that "with no-one in support/po" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with no-one in support/po = unattended.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 UNATTENDED mean?
UNATTENDED adjective- Not attended; without persons present.
- Not attended to; not receiving attention.