Guided by small light (3)
I believe the answer is:
led
This clue is a double definition.
'guided' is the first definition.
(similar in meaning)
'small light' is the second definition.
(light emitting diode)
'by' acts as a link.
(Other definitions for led that I've seen before include "Something emitting light" , "showed the way ahead" , "Came first" , "induced to" , "Took by the hand and showed the way" .)