One or many (4)

I believe the answer is:

unit

I'm a little stuck... Click here to teach me more about this clue!

'one' is the definition.
(synonyms)

I cannot understand how the remainder of the clue works.

(Other definitions for unit that I've seen before include "Individual thing, single and complete" , "Single thing or person" , "Individual item" , "Army division" , "Single person - group of people" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.