Evidence of fisticuffs in The Sun? (6)
I believe the answer is:
shiner
I believe this is a double definition.
'evidence of fisticuffs' is the first definition.
('shiner' can mean a bruise)
'the sun?' is the second definition.
(something which shines)
'in' acts as a link.
(Other definitions for shiner that I've seen before include "It may result from punch" , "injury to face?" , "Informal black eye - see how it glows" , "device that lightens one's work" , "Mouse" .)