The most common and most likely answer to this crossword clue is the 4 letter word WERE
I've seen this crossword clue in The Daily Telegraph
W
E
R
E
More clues leading to the result WERE
- Used to be a sort of wolf?
- Used to live close to meadow before
- Wife’s present: divorcing husband at one time past
- Had a life before wife turned up
- We are cut down or used to be
- We are – or used to be
- Used to be banks in both Whitstable and Ramsgate
- You and I are, or used to be
- Used to be the Telegraph crossword compilers? Touching!
- Lived in awe: redeemed
Buddy explains!

The straight part
We know that "Used to be" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case used to be = were.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 WERE mean?
WERE noun- A man, a husband
- A fine for slaying a man; weregild.
- The collective name for any kind of person that changes into another form under certain conditions, including the werewolf.