The most common and most likely answer to this crossword clue is the 5 letter word GROAN
G
R
O
A
N
More clues leading to the result GROAN
- Express dismay as relative has nothing to eat
- Grumble's increased audibly
- Complain when love concealed by relative
- Express exasperation when elderly relative pinches ring
- Nasty noise increased for listeners …
- Complaint that’s developed in one’s hearing?
- Good horse to audibly indicate distress
- Playing organ may cause complaint
- Good horse beef
- Swollen, we hear, producing bellyache
Buddy explains!

The straight part
We know that "Grumble" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case grumble = groan.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 GROAN mean?
GROAN noun- A low, mournful sound uttered in pain or grief.
- A low, guttural sound uttered in frustration, disapproval, or ecstasy.
- (of an object) A low creaking sound from applied pressure or weight.
- To make a groan.
- To strive after earnestly, as if with groans.