Warne's mysterious comeback (6)
I believe the answer is:
answer
'comeback' is the definition.
(I've seen this in another clue)
'warne's mysterious' is the wordplay.
'mysterious' indicates an anagram.
'warnes' with letters rearranged gives 'ANSWER'.
(Other definitions for answer that I've seen before include "Solution (to problem)" , "Reply or 8 across" , "See 9" , "'Daisy, Daisy, give me your ...... do'" , "fit" .)