Exclamation of annoyance (4)
I believe the answer is:
drat
'exclamation of annoyance' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for drat that I've seen before include "that expresses annoyance" , "Bother" , "Informal expression of annoyance" , "Mild expletive" , "Expression of mild annoyance" .)