Twinkling in private room reveals Screwtape, say (5)
I believe the answer is:
demon
'screwtape say' is the definition.
I can't judge whether this definition defines the answer.
'twinkling in private room' is the wordplay.
'twinkling' becomes 'mo' (both can mean a brief period of time).
'in' is an insertion indicator.
'private room' becomes 'den' (a secret room or location).
'mo' going into 'den' is 'DEMON'.
'reveals' is the link.
Can you help me to learn more?
(Other definitions for demon that I've seen before include "Evil spirit, devil" , "Imp" , "ace" , "Fiend, devil" , "Genius" .)