Fear adder’s movement (5)
I believe the answer is:
dread
'fear' is the definition.
(I know that fear can be written as dread)
'adder's movement' is the wordplay.
'movement' indicates anagramming the letters (letters move around).
'adder' with letters rearranged gives 'DREAD'.
(Other definitions for dread that I've seen before include "quail" , "Great fear or apprehension" , "Hairstyle" , "Anticipate with fear" , "Be afraid of - anxiety" .)