The sad mongrel - wretched pet (6,7)

I believe the answer is:
golden hamster
'pet' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'the sad mongrel wretched' is the wordplay.
'wretched' is an anagram indicator.
'the'+'sad'+'mongrel'='thesadmongrel'
'thesadmongrel' is an anagram of 'GOLDEN HAMSTER'.
Can you help me to learn more?
(Another definition for golden hamster that I've seen is " Rodent kept as a pet".)
