The most common and most likely answer to this crossword clue is the 5 plus 9 letter word PETTY CONSTABLE
P
E
T
T
Y
C
O
N
S
T
A
B
L
E
Buddy explains!
The straight part
We know that "old member of The Police" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old member of the police = petty constable.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.