Hospital situated in pleasant nook (5)
I believe the answer is:
niche
'nook' is the definition.
(I've seen this before)
'hospital situated in pleasant' is the wordplay.
'hospital' becomes 'H' (abbreviation for hospital on maps).
'situated in' indicates putting letters inside.
'pleasant' becomes 'nice' (similar in meaning).
'h' put within 'nice' is 'NICHE'.
(Other definitions for niche that I've seen before include "Particularly suitable position" , "small specialised market" , "Specialized market" , "comfortable situation" , "Suitable spot" .)