Puzzles formulated in games (7)
I believe the answer is:
enigmas
'puzzles' is the definition.
(I've seen this before)
'formulated in games' is the wordplay.
'formulated' indicates an anagram.
'in'+'games'='ingames'
'ingames' is an anagram of 'ENIGMAS'.
(Other definitions for enigmas that I've seen before include "They're mysterious or difficult to understand" , "'Mysteries, riddles (7)'" , "Problems" , "'Puzzles, riddles (7)'" , "Puzzles - mysteries" .)