New game in for puzzle (6)
I believe the answer is:
enigma
'puzzle' is the definition.
(thesaurus)
'new game in' is the wordplay.
'new' is an anagram indicator.
'game'+'in'='gamein'
'gamein' anagrammed gives 'ENIGMA'.
'for' is the link.
(Other definitions for enigma that I've seen before include "Something mysterious and puzzling" , "It's mysterious like gamine" , "Puzzle found in gem, Ian" , "Title of Elgar's set of variations" , "WW two Ger. code device; puzzle" .)