Still involved in tropical medicine (4)
I believe the answer is:
calm
'still' is the definition.
(I know that still can be written as calm)
'involved in tropical medicine' is the wordplay.
'involved in' indicates the answer is hidden within the clue.
'CALM' is hidden in the letters of 'tropical medicine'.
(Other definitions for calm that I've seen before include "Peaceful, not excited" , "Peaceful, tranquil" , "Composure or serenity" , "Placid and unruffled" , "'Tranquil, placid (4)'" .)