It was, however, as Charles Darwin's alter ego, anattack dog for the theory of evolution, that Huxley gained his greatest notoriety.
(figurative) A person or otherentity who fights physically on behalf of another.
2017 July 16, Brandon Nowalk, “Chickens and dragons come home to roost on Game Of Thrones (newbies)”, inThe Onion AV Club[1]:
In the middle of the night, snow falling all around, the Hound digs the family a grave. We didn’t need this episode to know the Hound has changed. Even if we hadn’t seen his relationship with Arya start to work its magic on him, the Hound’s time with the septon who saved him shows how far he’s come from the Lannisters’attack dog.
attack dog on Wikipedia.Wikipedia