General hospital getting a soldier upset (4)
I believe the answer is:
haig
'general' is the definition.
(Douglas Haig, WW1 general)
'hospital getting a soldier upset' is the wordplay.
'hospital' becomes 'h' (abbreviation for hospital on maps).
'getting' says to put letters next to each other.
'soldier' becomes 'gi' (GI can mean a US soldier).
'upset' says the letters should be written in reverse.
'gi' back-to-front is 'ig'.
'h'+'a'+'ig'='HAIG'
(Other definitions for haig that I've seen before include "Earl -; British WW 1 commander-in-chief" , "Douglas -, field marshal" , "British World War One field marshal" , "WWI C-in-C" .)