The most common and most likely answer to this crossword clue is the 6 letter word QUITCH
Q
U
I
T
C
H
Buddy explains!
The straight part
We know that "couch" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case couch = quitch.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 QUITCH mean?
QUITCH verb- To shake (something); to stir, move.
- To stir; to move.
- To flinch; shrink.
- Elymus repens, couch grass (a species of grass, often considered a weed)