The most common and most likely answer to this crossword clue is the 4 letter word RABI
R
A
B
I
More clues leading to the result RABI
Buddy explains!

The straight part
We know that "Harvest" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case harvest = rabi.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 RABI mean?
RABI noun- Spring.
- The spring harvest.