The most common and most likely answer to this crossword clue is the 8 letter word NOTIONAL
I've seen this crossword clue in The Times
N
O
T
I
O
N
A
L
More clues leading to the result NOTIONAL
- Ideal citizen displaying love for autocratic leader
- Out? A Liberal admitting nothing speculative
- Speculative but flawed consultation from which TUC’s withdrawn
- Speculative one stopping off, so to speak, by a loch
- Current cuts unacceptable — almost everything’s speculative
- Speculative first article in major newspaper’s replaced by nothing
- Somebody else supported by a line? Only in theory
- Fanciful Latin soon translated with no end of prowess
- Speculative citizen having made a trade for nothing
- No time left to tour Scottish island? That’s fanciful
Buddy explains!

The straight part
We know that "speculative" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case speculative = notional.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 NOTIONAL mean?
NOTIONAL noun- A fake company used as a front in espionage.
- Of, containing, or being a notion; mental or imaginary.
- Speculative, theoretical, not the result of research.
- Having descriptive value as opposed to a syntactic category.
- Used to indicate an estimate or a reference amount