Qualm about king's possible aircraft accident (5)
I believe the answer is:
prang
'possible aircraft accident' is the definition.
(prang can mean a vehicle crash)
'qualm about king's' is the wordplay.
'qualm' becomes 'pang' (I've seen this in another clue).
'about' is an insertion indicator.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'pang' placed around 'r' is 'PRANG'.
(Other definitions for prang that I've seen before include "Car collision" , "Plane or car crash" , "Possible argument with van" , "Popularly, a motoring contretemps" , "Bomb attack" .)