Actuator

2 clues
Relay device
Mechanism that switches something on — autocrat (anag)
Similar answers:
Abator
Abators
Abbreviator
Abdicator
Abdicators
Abnegator
Abnegators
Abrogator
Accelerator
Activator
Actu
Actual
Actualfact
Actualists
Actualities
Actuality
Actualize
Actually
Actuallybutit
Actualprice