A ___ in the machine (3)
I believe the answer is:
cog
(Other definitions for cog that I've seen before include "that engages with others in revolution" , "Machine wheel" , "Gear-tooth" , "Wheel with projections" , "Junior official" .)
I believe the answer is:
cog
(Other definitions for cog that I've seen before include "that engages with others in revolution" , "Machine wheel" , "Gear-tooth" , "Wheel with projections" , "Junior official" .)