The most common and most likely answer to this crossword clue is the 11 letter word SPECULATIVE
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More clues leading to the result SPECULATIVE
Buddy explains!

The straight part
We know that "involving guesswork" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case involving guesswork = speculative.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 SPECULATIVE mean?
SPECULATIVE adjective- Characterized by speculation; based on guessing, unfounded opinions, or extrapolation.
- Pursued as a gamble, with possible large profits or losses; risky.
- Pertaining to financial speculation; Involving or resulting from high-risk investments or trade.