The most common and most likely answer to this crossword clue is the 6 letter word FIBRES
I've seen this crossword clue in The Guardian
F
I
B
R
E
S
Buddy explains!
The straight part
We know that "They may be a (sic) spun" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they may be a (sic) spun = fibres.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 FIBRES mean?
FIBRES noun- A single piece of a given material, elongated and roughly round in cross-section, often twisted with other fibres to form thread.
- Material in the form of fibres.
- Dietary fibre.
- Moral strength and resolve.
- The preimage of a given point in the range of a map.
- Said to be of a morphism over a global element: The pullback of the said morphism along the said global element.
- A kind of lightweight thread of execution.
- A long tubular cell found in muscle tissue; myocyte.