Black eye, informally (6)
I believe the answer is:
shiner
'black eye informally' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for shiner that I've seen before include "Mouse" , "Possible end of scrapping" , "device that lightens one's work" , "Black eye - small glittering fish" , "Informal black eye - see how it glows" .)