The most common and most likely answer to this crossword clue is the 9 letter word OVERSTATE
I've seen this crossword clue in Financial Times
O
V
E
R
S
T
A
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More clues leading to the result OVERSTATE
- Exaggerate deliveries going to art gallery
- Garbage in Sappho’s last poem to stretch truth
- Exaggerate aspect of proceedings from Lord’s gallery?
- Exaggerate about involving government
- Exaggerate position of country’s ruler
- Make too much of condition after having finished first
- Exaggerate past situation
- Exaggerate, so the Queen rules on, say
- Blow up at least 12 deliveries to gallery
- Exaggerate ancient history on nation
Buddy explains!

The straight part
We know that "to stretch truth" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to stretch truth = overstate.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 OVERSTATE mean?
OVERSTATE verb- To exaggerate; to state or claim too much.