Club race in pure chaos! (6)
I believe the answer is:
putter
'club' is the definition.
(a golf club)
'race in pure chaos' is the wordplay.
'race' becomes 'tt'.
'in' is an insertion indicator.
'chaos' indicates an anagram.
'pure' with letters rearranged gives 'puer'.
'tt' put into 'puer' is 'PUTTER'.
(Other definitions for putter that I've seen before include "Club to use on the green" , "Type of golf club" , "Club used on the green" , "Golf club used on greens" , "Golf-club" .)