Automatic control device changes revs with ring (5)
I believe the answer is:
servo
'automatic control device' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'changes revs with ring' is the wordplay.
'changes' is an anagram indicator.
'with' is a charade indicator (letters next to each other).
'ring' becomes 'o'.
'revs' is an anagram of 'serv'.
'serv'+'o'='SERVO'
Can you help me to learn more?
(Other definitions for servo that I've seen before include "car mechanism" , "Amplifying motor" , "Control motor" , "Assisting motor" , "Mechanism amplifying motion" .)