The most common and most likely answer to this crossword clue is the 6 letter word RENNET
I've seen this crossword clue in Financial Times
R
E
N
N
E
T
More clues leading to the result RENNET
- Return of banknote, which may be in Leicester, say
- Setter demanding cashback?
- Send up note for producer of junket
- Note upcoming cheese agent
- Note round variety of apple
- Note about what cheese-maker needs
- Cheesemakers use this apple
- Send up note to get ingredient for cheesemaking
- Bank note returned
- Separatist agent’s revolutionary note
Buddy explains!

The straight part
We know that "Cheesemakers use this/apple" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cheesemakers use this/apple = rennet.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 RENNET mean?
RENNET noun- An enzyme used as the first step in making cheese, to curdle the milk and coagulate the casein in it, derived by soaking the fourth stomach of a milk-fed calf in brine.
- Any of various kinds of apple, mostly of French origin, characterized by russeting.