Smirking, about to annoy (3)
I believe the answer is:
irk
'to annoy' is the definition.
(I've seen this before)
'smirking about' is the wordplay.
'about' says the answer is hidden in the clue (the clue goes around or about the answer).
'IRK' is hidden in the letters of 'smirking'.
(Other definitions for irk that I've seen before include "Irritate, annoy" , "cause annoyance" , "English river" , "Get at" , "Irritate, vex" .)