The most common and most likely answer to this crossword clue is the 9 letter word MONOCULAR
I've seen this crossword clue in The Guardian
M
O
N
O
C
U
L
A
R
More clues leading to the result MONOCULAR
Buddy explains!

The straight part
We know that "Like Nelson" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case like nelson = monocular.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 MONOCULAR mean?
MONOCULAR noun- A monocle.
- (retronym) A monocular telescope, as opposed to binoculars.
- Having one eye.
- Related to a monocle.
- Of any optical system suitable for use by one eye at a time.