It may mean you've been sickened by the ham (7)
I believe the answer is:
catcall
'it may mean you've been sickened' is the definition.
The definition suggests a singular noun which matches the answer.
'by the ham' is the wordplay.
I cannot really understand how this works, but
'by' could be 'at' and 'at' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for catcall that I've seen before include "Mocking remark" , "Mocking shout or whistle" , "Derisive call" , "Barracking" , "Audibly disapprove" .)