Policeman circling hospital in helicopter (7)
I believe the answer is:
chopper
'helicopter' is the definition.
('chopper' can be a synonym of 'helicopter')
'policeman circling hospital in' is the wordplay.
'policeman' becomes 'copper' (copper is a kind of policeman).
'circling hospital' becomes 'h' (I am not sure about the 'circling' bit.**).
'in' means one lot of letters goes inside another.
'copper' going around 'h' is 'CHOPPER'.
Can you help me to learn more?
(Other definitions for chopper that I've seen before include "that comes down on the block?" , "Helicopter (sl.)" , "Motorbike" , "Hatchet" , "An axe, or a slang helicopter" .)