Boy joins workers' organisation in US city (6)
I believe the answer is:
tucson
'us city' is the definition.
(I've seen this before)
'boy joins workers' organisation' is the wordplay.
'boy' becomes 'son' (synonyms).
'joins' means one lot of letters go next to another.
'workers' organisation' becomes 'tuc' (I can't explain this - if you can you should believe this answer much more).
'son' after 'tuc' is 'TUCSON'.
'in' is the link.
Can you help me to learn more?
(Other definitions for tucson that I've seen before include "City in 9" , "Arizonan city" , "US city" , "Arizona city that counts badly" , "American city" .)