By now cryptid must be finally dismissed (3)
I believe the answer is:
yet
'by now' is the definition.
('yet' can mean 'up to this point' or 'by now')
'cryptid must be finally dismissed' is the wordplay.
'cryptid' becomes 'yeti' (yeti is an example).
'must be finally dismissed' means to remove the last letter.
'yeti' with its final letter taken off is 'YET'.
(Other definitions for yet that I've seen before include "Although" , "Up to the present time" , "Though; still" , "in spite of that" , "Up to this time and continuing" .)