Cleaner vehicle outside hospital (4)
I believe the answer is:
char
'cleaner' is the definition.
(I've seen this before)
'vehicle outside hospital' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle**).
'outside' indicates putting letters inside.
'hospital' becomes 'h'.
'car' placed around 'h' is 'CHAR'.
(Other definitions for char that I've seen before include "Burn lightly" , "Fish < tea" , "Scorch, small fish" , "(Work as a) cleaner" , "Make black by burning, say toast" .)