Still finding some mythical monsters (4)
I believe the answer is:
calm
'still' is the definition.
(I know that still can be written as calm)
'some mythical monsters' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'CALM' is hidden in the letters of 'mythical monsters'.
'finding' is the 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" .)