The most common and most likely answer to this crossword clue is the 7 letter word SATSUMA
I've seen this crossword clue in The Guardian
S
A
T
S
U
M
A
More clues leading to the result SATSUMA
- Posed a gripping problem, something to get your teeth into!
- Tot tucked into Eastern meat dish having no yen for fruit
- Take up something most essential, as for citrus fruit
- Fruit essential while travelling west
- Mandarin tests Ms. Thurman
- Wobbly ass and a tum that’s segmented
- A prerequisite when around fruit
- Squatted on whole area for fruit
- Orange lot rounded up by day one
- Source of Vitamin C vital when suffering relapse
Buddy explains!

The straight part
We know that "Source of Vitamin C/Source of Vitamin C" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case source of vitamin c/source of vitamin c = satsuma.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 SATSUMA mean?
SATSUMA noun- A seedless and easy-peeling cultivar of mandarin orange of Japanese origin; Citrus unshiu.