Absolute twist in tail describing Spieth's second round (6)
I believe the answer is:
sphere
'round' is the definition.
(thesaurus)
'absolute twist in tail describing spieth's second' is the wordplay.
I cannot quite understand how this works, but
'second' could be 're' (prefix meaning second in eg review, re-education) and 're' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for sphere that I've seen before include "Orb or globe" , "Round object" , "Province - range" , "Perfect round" , "Globe or ball" .)