Resistance/current gradient? (4)
I believe the answer is:
ramp
'gradient?' is the definition.
(I've seen this in another clue)
I can't explain the rest of the clue.
(Other definitions for ramp that I've seen before include "It gets travellers off" , "Inclined plane; swindle" , "Slope for a pram" , "fleece?" , "what could be criminal offence" .)