It stimulates an immune response like gargling neat gin (7)
I believe the answer is:
antigen
'it stimulates an immune response' is the definition.
The definition suggests a singular noun which matches the answer.
'gargling neat gin' is the wordplay.
'neat gin' can be anagrammed to 'ANTIGEN'.
However, I'm not clear how the anagram is indicated.
'like' acts as a link.
Can you help me to learn more?
(Other definitions for antigen that I've seen before include "Something inducing an immune response, neat gin (anag.)" , "It stimulates immune responses - tag nine (anag)" , "toxin" , "Substance inducing an immune response" , "Biological substance" .)