Just a marginal cough? (4)
I believe the answer is:
ahem
'just a marginal cough?' is the definition.
I can't judge whether this defines the answer.
'a marginal cough?' is the wordplay.
'marginal cough?' becomes 'hem' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a'+'hem'='AHEM'
Can you help me to learn more?
(Other definitions for ahem that I've seen before include "Expression of disapproval" , "Attention-getter" , "Sound made when clearing throat" , "Throat-clearing noise?" , "Polite word to draw attention" .)