The most common and most likely answer to this crossword clue is the 7 letter word STAUNCH
I've seen this crossword clue in The Times
S
T
A
U
N
C
H
More clues leading to the result STAUNCH
Buddy explains!

The straight part
We know that "It’s true" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s true = staunch.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 STAUNCH mean?
STAUNCH verb- To stop the flow of (blood).
- To stop, check, or deter an action.
- Loyal, trustworthy, reliable.
- Dependable, persistent.