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' says the answer is hidden in the clue.
'CALM' can be found hidden inside '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)'" .)