Current went through transformer coil (5)
I believe the answer is:
twine
'coil' is the definition.
(I've seen this before)
'current went through transformer' is the wordplay.
I cannot quite see how this works, but
'current' could be 'in' ('in' can mean current or trendy) and 'in' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for twine that I've seen before include "Tough string" , "Knot" , "weaving" , "String, cord" , "Twisted cord" .)