A "shiner", it seems, makes one scowl (6)
I believe the answer is:
glower
'one scowl' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for glower that I've seen before include "Angry stare" , "shiner?" , "Frown" , "Threatening look" , "Glare" .)