The most common and most likely answer to this crossword clue is the 4 plus 4 letter word CUBE ROOT
I've seen this crossword clue in The Guardian
C
U
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T
More clues leading to the result CUBE ROOT
- 3 is 27’s cue to rob cast
- Two of eight, perhaps, heading for unrest in October after revolution
- Prompt monster to report mathematical value
- Bird taking taxi, as 3 of 27
- Prompt Yahoo to report mathematical value
- Two for eight, perhaps — it’s a factor
- 9’s works out at 3
- – in relation to 1728
- Number to be found in old city entertained by crazy fellow
- a One is one’s own man, no longer leading Englishmen behind block
Buddy explains!
The straight part
We know that "Two of eight, perhaps," is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case two of eight, perhaps, = cube root.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.