The most common and most likely answer to this crossword clue is the 4 letter word TROY
I've seen this crossword clue in The Times
T
R
O
Y
More clues leading to the result TROY
- Former city politician has a change of heart
- City, once, score without ball
- City score, retaining ball
- Attempt to keep old system of weights
- Effort to retain old weight system
- Attempt to introduce the second of horses here?
- Ancient city’s weight system for metals
- Play about Romeo where great beauty held captive
- Plague grips ordinary ancient city
- Old city Conservative upset his constituents!
Buddy explains!

The straight part
We know that "Former city" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case former city = troy.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 TROY mean?
TROY adjective- Of, or relating to, troy weight.