Noun I write out to describe the workers (5)

I believe the answer is:

union

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

'describe the workers' is the definition.
I can't judge whether this definition defines the answer.

'noun i write out' is the wordplay.
'noun i' can be anagrammed to 'UNION'.
But, I am not clear how this is indicated.

'to' acts as a link.

Can you help me to learn more?

(Other definitions for union that I've seen before include "Marriage; trade assoc." , "Climbing plant" , "Association with a common purpose" , "match" , "Workers' association - marriage" .)

I've seen this clue in The Irish Independent.

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.