Perhaps a dog? Move in, or run away (8)
I believe the answer is:
omnivore
'run away' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'perhaps a dog? move in or' is the wordplay.
'move in or' can be anagrammed to 'OMNIVORE'.
Though, I'm not clear how this is indicated.
Can you help me to learn more?
(Other definitions for omnivore that I've seen before include "who'll swallow anything?" , "Animal that eats any type of food" , "I'll take in anything" , "Meat and veg eater" , "Creature eating any type of food" .)