Germs probably function here, initiating in guts (8)
I believe the answer is:
bacteria
'germs' is the definition.
(I've seen this in another clue)
'probably function here initiating in guts' is the wordplay.
I cannot quite see how this works, but
'function' could be 'act' (I've seen this in another clue) and 'act' is located in the answer.
The remaining letters 'beria' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bacteria that I've seen before include "Tiny organisms, may be good or bad" , "Care a bit about these micro-organisms" , "Infectious organisms" , "Possible cause of disease" , "Caberet I perform for the tiny organisms" .)