Autocrat, possibly one initiating operation (8)
I believe the answer is:
actuator
'one initiating operation' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'autocrat possibly' is the wordplay.
'possibly' indicates anagramming the letters.
'autocrat' is an anagram of 'ACTUATOR'.
Can you help me to learn more?
(Other definitions for actuator that I've seen before include "Something initiating operation" , "A mechanism that causes something to operate" , "Mechanism that switches something on -- autocrat (anag)" , "Mechanism causing operation" , "Something causing operation" .)