Blank flier secretary placed in study ... (7)
I believe the answer is:
deadpan
'blank' is the definition.
(I've seen this before)
'flier secretary placed in study' is the wordplay.
'flier secretary' becomes 'adpa' (I can't explain this - if you can you should believe this answer much more).
'placed in' indicates putting letters inside (I've seen this in other clues).
'study' becomes 'den' (term for a study or office).
'adpa' inserted inside 'den' is 'DEADPAN'.
Can you help me to learn more?
(Other definitions for deadpan that I've seen before include "Poker-faced" , "without a flicker" , "With expressionless face" , "Showing no expression" , "showing no emotion" .)