One opposing current measures is tortured to some extent (8)
I believe the answer is:
resistor
'one opposing current' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'measures is tortured to some extent' is the wordplay.
'to some extent' indicates the answer is hidden within the clue.
'RESISTOR' is hidden within 'measures is tortured'.
Can you help me to learn more?
(Other definitions for resistor that I've seen before include "Circuit component" , "It obstructs current" , "Electronic component" , "Manipulator of current" , "Electrical component" .)