Clue: Sort of boomerang likely to lose line and deviate (5)
Answer: KYLIE
Explanation: Definition: Sort of boomerang
An anagram ('deviate') of '[l]ikely' minus one of the Ls ('to lose line'). KYLIE and KILEY are alternative spellings, and alternative anagrams, and it needs 27A ('or a lucky guess) to see which is required.