Heads of government agency played iPhone's new games, yawning (6)
I believe the answer is:
gaping
'yawning' is the definition.
(synonyms)
'heads of government agency played iphone's new games' is the wordplay.
'heads of' suggests taking the first letters.
The initial letters of 'government agency played iphones new games' is 'GAPING'.
(Other definitions for gaping that I've seen before include "Yawning" , "Staring open-mouthed" , "Opening mouth wide or staring in wonder" , "With the mouth wide open, in wonder perhaps" .)