The most common and most likely answer to this crossword clue is the 10 letter word CODSWALLOP
I've seen this crossword clue in The Guardian
C
O
D
S
W
A
L
L
O
P
More clues leading to the result CODSWALLOP
- Batter fish first then start to steam rhubarb
- Lettuce and beer tucked into by daughter, 20
- Nonsense to poke fun at small beer
- Small beer to accompany fish, or tripe
- Fish supper without superior beer is rubbish
- Rubbish records about love by Wham!
- Fool was confused by overturned vote? That’s rubbish
- Rubbish kind of dive not completed by swimmer, ending in heap
- Sham bribe to cross border, rubbish
- Fake concession over Trump pledge is nonsense
Buddy explains!

The straight part
We know that "nonsense" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nonsense = codswallop.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 CODSWALLOP mean?
CODSWALLOP noun- Senseless talk or writing; nonsense; rubbish.
- Used to express disbelief: nonsense!; rubbish!