Current should be introduced to belted saw (5)
I believe the answer is:
spied
'saw' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for spied that I've seen before include "Saw" , "Caught sight of" , "Watched secretly" , "Was a secret agent" , "Seen" .)