Flap in one’s in-tray (2-2)
I believe the answer is:
to-do
This clue is a double definition.
'flap' is the first definition.
(I've seen this before)
'one's in-tray' is the second definition.
(things waiting to be done)
'in' acts as a link.
(Other definitions for to-do that I've seen before include "Bustle" , "Quarrel" , "Fuss and bother" , "Fuss or commotion" , "Kerfuffle" .)