Putting one over on the syndicate (5)
I believe the answer is:
union
'syndicate' is the definition.
(I know that union is a type of syndicate)
'putting one over on' is the wordplay.
'putting one over' becomes 'uni' (I can't explain this - if you can you should give a lot more credence to this answer).
'uni'+'on'='UNION'
'the' is the link.
Can you help me to learn more?
(Other definitions for union that I've seen before include "Coupling, merger" , "political alliance" , "Workers' federation" , "Trade organisation to represent workers" , "America" .)