Showing off is fair (8)
I believe the answer is:
sporting
This clue is a double definition.
'showing off' is the first definition.
(as in sporting or showing off an item of clothing)
'fair' is the second definition.
(similar in meaning)
'is' acts as a link.
(Other definitions for sporting that I've seen before include "Diver's point of departure" , "Fair and generous" , "Fair (chance)" , "Able to take defeats in good part" , "game" .)