The most common and most likely answer to this crossword clue is the 2 plus 3 letter word MY EYE
I've seen this crossword clue in The Times
M
Y
E
Y
E
More clues leading to the result MY EYE
- Bit of me, you and the old nonsense!
- Nonsense from Monsieur you repeated
- It helps me perceive an exclamation of surprise
- Through which I see rubbish
- Organ belonging to me? That's not true
- With which I perceive an expression of disbelief
- Millions with open-ended agreements? I think not
- Might have an Apple? I hardly think so!
- Boatman’s Boatman, you say? I don’t agree!
- Did you ever mark articles in the past?
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 = my eye.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.