The most common and most likely answer to this crossword clue is the 3 letter word COT
C
O
T
Buddy explains!
The straight part
We know that "Function" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case function = cot.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 COT mean?
COT noun- A simple bed, especially one for portable or temporary purposes.
- A bed for infants or small children, with high, often slatted, often moveable sides.
- A wooden bed frame, slung by its corners from a beam, in which officers slept before the introduction of bunks.
- A cottage or small homestead.
- A pen, coop, or similar shelter for small domestic animals, such as sheep or pigeons.
- A small, crudely-formed boat.
- A cover or sheath; a fingerstall.