Doctor coming up with hospital gets some resistance (3)
I believe the answer is:
ohm
'some resistance' is the definition.
(I've seen this in another clue)
'doctor coming up with hospital' is the wordplay.
'doctor' becomes 'mo' (medical officer).
'coming up' says the letters should be written in reverse (in a down clue, letters go up).
'with' is an insertion indicator.
'hospital' becomes 'H' (abbreviation for hospital on maps).
'mo' in reverse letter order is 'om'.
'om' enclosing 'h' is 'OHM'.
'gets' is the link.
(Other definitions for ohm that I've seen before include "SI unit of electrical resistance" , "measure of resistance" , "A little resistance" , "Physicist" , "physical unit" .)