The most common and most likely answer to this crossword clue is the 12 letter word ASPIRATIONAL
I've seen this crossword clue in The Sunday Telegraph
A
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More clues leading to the result ASPIRATIONAL
- Pertaining to hopes, when very good and reasonable
- Organised PA is reasonable and ambitious
- Hoping to get a small ratio using integers
- Ambitious and venomous reptile – one that’s intelligent
- Ambitious and venomous reptile, one that’s intelligent
- A flashy black market hawker not against thinking of lofty aims and hopes
- Relating to hope, since religious and sensible
Buddy explains!

The straight part
We know that "Relating to hope" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case relating to hope = aspirational.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 ASPIRATIONAL mean?
ASPIRATIONAL noun- A person with aspirations.
- Being ambitious.
- Desiring success.
- Expressing a hope or intention but not creating a legally binding obligation.