Puzzle spread in game (6)
I believe the answer is:
enigma
'puzzle' is the definition.
(I've seen this before)
'spread in game' is the wordplay.
'spread' indicates anagramming the letters.
'in'+'game'='ingame'
'ingame' with letters rearranged gives 'ENIGMA'.
(Other definitions for enigma that I've seen before include "cryptic puzzle!" , "Mysterious person" , "Riddle - German coding machine" , "Solution to mystery" , "closed book" .)