Groan from US soldier keeling over in southern hospital (4)
I believe the answer is:
sigh
'groan' is the definition.
(I've seen this before)
'us soldier keeling over in southern hospital' is the wordplay.
'us soldier' becomes 'gi' (I've seen this in other clues).
'keeling over' is a reversal indicator.
'in' indicates putting letters inside.
'southern' becomes 's' (abbreviation).
'hospital' becomes 'h'.
'gi' backwards is 'ig'.
's'+'h'='sh'
'ig' placed within 'sh' is 'SIGH'.
'from' acts as a link.
(Other definitions for sigh that I've seen before include "Vocal expression of weariness" , "Release a long breath" , "Express dejection" , "Breathe despondently" , "Express relief or sorrow" .)