Current conductor left inside motor starter (9)
I believe the answer is:
maelstrom
'current' is the definition.
(I know that maelstrom is a type of current)
'conductor left inside motor starter' is the wordplay.
'conductor' becomes 'maestro' (I've seen this in another clue).
'left' becomes 'l' (common abbreviation).
'inside' is an insertion indicator.
'starter' says to take the initial letters.
The initial letter of 'motor' is 'm'.
'maestro' placed around 'l' is 'maelstro'.
'maelstro'+'m'='MAELSTROM'
(Other definitions for maelstrom that I've seen before include "Strong circular current of water" , "disorder" , "Powerful whirlpool" , "Powerful circular current of water" , "Confused situation" .)