The most common and most likely answer to this crossword clue is the 5 letter word WHINE
I've seen this crossword clue in Financial Times
W
H
I
N
E
More clues leading to the result WHINE
- Grumble when husband gets in hock, perhaps
- Peevish complaint from Caucasian changing time to noon
- Horse served in Bordeaux perhaps causing belly-ache
- Graves possibly heard to complain
- Moan, if drink’s drunk hot
- Plaintive cry from husband entering port, perhaps
- Drink husband imbibed brings complaint
- Claret possibly poured out for beef
- Complaining cry from first of holidaymakers entering Bordeaux?
Buddy explains!

The straight part
We know that "complain" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case complain = whine.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 WHINE mean?
WHINE noun- A long-drawn, high-pitched complaining cry or sound
- A complaint or criticism
- To utter a high-pitched cry.
- To make a sound resembling such a cry.
- To complain or protest with a whine or as if with a whine.
- To move with a whining sound.
- To utter with the sound of a whine.