The final unruly coil in intestinal bacteria (1,4)
I believe the answer is:
e coli
'intestinal bacteria' is the definition.
The definition suggests a singular noun which matches the answer.
'the final unruly coil' is the wordplay.
'final' indicates one should take the final letters.
'unruly' indicates anagramming the letters.
The last letter of 'the' is 'e'.
'coil' anagrammed gives 'coli'.
'e'+'coli'='E COLI'
'in' is the link.
Can you help me to learn more?
(Other definitions for e coli that I've seen before include "Gut bugs" , "cause of illness" , "Common species of bacterium" , "An infection found in food and water" , "Cause of infection" .)