An expression of contempt, we hear (3)
I believe the answer is:
bah
'an expression of contempt' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for bah that I've seen before include "Exclamation of disgust or annoyance" , "Exclamation of contempt or disgust - Scrooge used to say it" , "Disbelieving expression" , "''...! Humbug!'' (Scrooge)" , "Comic expression of contempt" .)