Pass German egg sandwiches that might make him sick (1,4)
I believe the answer is:
e coli
'german egg sandwiches that might make him sick' is the definition.
The definition suggests a singular noun which matches the answer.
'pass' is the wordplay.
I cannot quite understand how this works, but
'pass' could be 'col' (col is a term for a mountain pass) and 'col' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for e coli that I've seen before include "An infection found in food and water" , "cause of serious complaint" , "Nasty bug" , "Cause of internal problem" , "Type of bacteria causing food poisoning" .)