### Clue: How Brexit begins with hopeless nationalist (5)
### Answer: BLIMP 
 ### Explanation: Definition: nationalist
 **1st letter of**(How … begins) "Brexit" **plus**(with) LIMP(hopeless/useless).
Answer: Colonel Blimp, a cartoon character who was jingoistic and stereotypically British, whom you might call a nationalist, right or wrong. **
I liked the undertones of the clue's surface.