Is "a-blink" an adjectival form of "blink" in old days?

Under his breath, with a furtive exultation, he began once again the paean of victory and devastation. And presently his eyes were rewarded: out through that doorway came a long, low, yellow-and-brown beast, with eyes a-blink at the waning daylight, and dark wet stains around the fur of jaws and throat.

I can’t find this "a-blink" in the dictionary, so I presume this word is no longer in use. Is it an adjectival form of "blink"? And could it be replaced by blinking these days?