Still finding some mythical monsters (4)
I believe the answer is:
'still' is the definition.
(I know that still can be written as calm)
'some mythical monsters' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'CALM' is hidden in the letters of 'mythical monsters'.
'finding' acts as a link.
(Other definitions for calm that I've seen before include "Controlled, not agitated" , "Composure or serenity" , "Still and quiet" , "'Tranquil, placid (4)'" , "Imperturbable, soothe" .)