Cross mongrel (6)
I believe the answer is:
hybrid
I believe this is a double definition.
'cross' is the first definition.
(thesaurus)
'mongrel' is the second definition.
(thesaurus)
(Other definitions for hybrid that I've seen before include "Offspring of mixed parents" , "A composite of mixed origin" , "Plant that is the offspring of two different species" , "Like a mule" , "(One) of mixed origin" .)