Clue: Boris's hair? Prime minister cut the ends off (6)
Answer: THATCH
Explanation: Definition: Boris's hair
This did not strike me as the best introduction for a new setter, althought the reference in the definition to presages a homorous slant to the setter's clues.. The wordplay, however, is questionable: THATCH[er] ('Prime minister') minus the last two letters ('cut the ends off', which would normally indicate the first and last, rather than the last two). Maybe it is worth a little indulgence for the joke.