Mislaying (6)
I believe the answer is:
losing
'mislaying' is the definition.
('lose' can be a synonym of 'mislay')
This is the entire clue.
(Other definitions for losing that I've seen before include "Logs in (anag.)" , "Opposite of 9" , "Failing to keep" , "Behind in a competition" , "Spice" .)