The most common and most likely answer to this crossword clue is the 7 letter word PEEVISH
I've seen this crossword clue in The Sunday Telegraph
P
E
E
V
I
S
H
Buddy explains!
The straight part
We know that "grumpy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case grumpy = peevish.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 PEEVISH mean?
PEEVISH adjective- Characterized by or exhibiting petty bad temper, bad-tempered, moody, cross.
- Constantly complaining, whining; childishly fretful.
- Easily annoyed, especially by things that are not important; irritable, querulous.
- (adverb) Peevishly.
- Clever, expert.
- Sharp, piercing, bitter (of the wind); windy, blustery (of the weather).
- Perverse, refractory; headstrong, obstinate; capricious, skittish; (also) coy.
- Silly, senseless, foolish.
- Beside oneself; out of one's senses; mad.
- Spiteful, malignant, mischievous, harmful.
- Hateful, distasteful, horrid.