Track parking at hospital (4)
I believe the answer is:
path
'track' is the definition.
(synonyms)
'parking at hospital' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'hospital' becomes 'h' (abbreviation for hospital on maps).
'p'+'at'+'h'='PATH'
(Other definitions for path that I've seen before include "Track; direction" , "Pavement" , "Walkway" , "Will's go" , "Bridleway" .)