Recoil once from bloody Eastender's dog (7)
I believe the answer is:
redound
'recoil once' is the definition.
(redound could historically mean to recoil)
'from bloody eastender's dog' is the wordplay.
I cannot really understand how this works, but
'from' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
'bloody' could be 'red' and 'red' is found in the answer.
The remaining letters 'und' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for redound that I've seen before include "come back?" , "return" , "Contribute (to a person's honour)" , "Recoil from" .)