"Uh ... pardon me" (4)
I believe the answer is:
ahem
'uh pardon me' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ahem that I've seen before include "Throat clearance to attract attention" , "call attracting attention" , "Sound made when clearing throat" , "I say!" , "Polite word to draw attention" .)