The most common and most likely answer to this crossword clue is the 5 letter word MELON
I've seen this crossword clue in The Guardian
M
E
L
O
N
More clues leading to the result MELON
Buddy explains!

The straight part
We know that "is it/?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case is it/? = melon.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 MELON mean?
MELON noun- Any of various plants of the family Cucurbitaceae grown for food, generally not including the cucumber.
- The fruit of such plants.
- A light pinkish orange colour, like that of some melon flesh.
- (usually in the plural) Breasts.
- The head.
- A member of the Green Party, or similar environmental group.
- A mass of adipose tissue found in the forehead of all toothed whales, used to focus and modulate vocalizations.
- Of a light pinkish orange colour, like that of melon flesh.
- The result of heptazine being polymerized with the tri-s-triazine units linked through an amine (NH) link.