Core position of hospital in NHS (6)
I believe the answer is:
middle
'core' is the definition.
(I know that core can be written as middle)
I can't explain the remainder of the clue.
(Other definitions for middle that I've seen before include "Group of clubs; distance" , "Centre or core" , "Heart" , "Intermediate" , "It's equidistant from the extremes" .)