Rodent's sudden movement when dodging king snake (6)
I believe the answer is:
jerboa
'rodent's' is the definition.
(jerboa is a kind of rodent)
'sudden movement when dodging king snake' is the wordplay.
'sudden movement' becomes 'jerk' (I've seen this in another clue).
'when dodging' suggests deleting specific letters.
'king' becomes 'K' (chess abbreviation).
'snake' becomes 'boa' (boa constrictor, type of snake).
'jerk' with 'k' taken out is 'jer'.
'jer'+'boa'='JERBOA'
(Other definitions for jerboa that I've seen before include "Mouse-like jumping rodent - ear job (anag)" , "Desert-dwelling rodent" , "Desert rodent" .)