Still half sick, left hospital department (6)
I believe the answer is:
silent
'still' is the definition.
('silent' can be a synonym of 'still')
'half sick left hospital department' is the wordplay.
'half' indicates taking half.
'left' becomes 'l' (common abbreviation).
'hospital department' becomes 'ent'.
'sick' halved is 'si'.
'si'+'l'+'ent'='SILENT'
(Other definitions for silent that I've seen before include "Quiet -- 13 (anag)" , "Not speaking" , "Listen, being speechless after 10 across" , "Listen (anag.)" , "Making no sound" .)