Throat-clearing sound (4)
I believe the answer is:
ahem
'throat-clearing sound' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ahem that I've seen before include "Cough to draw attention" , "Sound used to attract attention" , "attempt to attract attention" , "Throat clearance to attract attention" , "Polite noise to draw attention" .)