### Clue: Union pledge to fight cartel (10,4)
### Answer: ENGAGEMENT RING 
 ### Explanation: Definition: Union pledge
 ENGAGEMENT(a fight) + RING(a cartel;a group with a common purpose, usually an illegal one).
Defn: Cryptically, a symbol of one's pledge to unite in marriage in the future, the cost of which, one might say, is the first of your union dues.