One day in this place and crazy with no union supporters (9)
I believe the answer is:
adherents
'supporters' is the definition.
(I've seen this before)
'one day in this place and crazy with no union' is the wordplay.
'one day in this place' becomes 'adhere' (I am not sure about this - if you are sure you should believe this answer much more).
'and' is a charade indicator (letters next to each other).
'crazy' becomes 'nuts' (nuts can informally mean crazy or mad).
'with no' suggests deleting specific letters.
'union' becomes 'U' (common abbreviation as in 'Trades Union Congress').
'nuts' with 'u' removed is 'nts'.
'adhere'+'nts'='ADHERENTS'
Can you help me to learn more?
(Other definitions for adherents that I've seen before include "Followers" , "Supporters of neat herds" , "'Supporters, disciples (9)'" , "Supporters of neatherds" .)