The most common and most likely answer to this crossword clue is the 7 letter word POLECAT
I've seen this crossword clue in Independent
P
O
L
E
C
A
T
More clues leading to the result POLECAT
- Place to set free American skunk
- Place to free smelly mammal
- Animal caught in field, hiding in grass
- European jazz fan, one raising quite a stink!
- Survey reported on queen, say, is source of stink
- Smelly animal’s head discussed – about time
- Staff whip smelly animal
- Best to adopt expert line when rearing mammal
- Skunk or European lynx?
- European hypocrisy dismissing new mammal
Buddy explains!

The straight part
We know that "old prostitute" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old prostitute = polecat.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 POLECAT mean?
POLECAT noun- A weasel-like animal of the genus Mustela.
- A skunk.
- A tubular device used to support lights on a set.