The most common and most likely answer to this crossword clue is the 10 letter word BELLYACHES
I've seen this crossword clue in The Guardian
B
E
L
L
Y
A
C
H
E
S
More clues leading to the result BELLYACHES
Buddy explains!
The straight part
We know that "Persistent complaints" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case persistent complaints = bellyaches.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 BELLYACHES mean?
BELLYACHES noun- Any pain in the belly, stomach, or abdomen.
- To unnecessarily complain or whine, often about simple matters.