Retro graffiti unnervingly captures discontent (5)
I believe the answer is:
ennui
'discontent' is the definition.
(ennui is a feeling of boredom or discontent)
'retro graffiti unnervingly captures' is the wordplay.
'retro' says the letters should be written in reverse (retro is Latin for 'backwards').
'captures' says the answer is hidden in the clue (the answer is trapped within the clue).
'iunne' is hidden in the letters of 'graffiti unnervingly'.
'iunne' reversed gives 'ENNUI'.
(Other definitions for ennui that I've seen before include "Boredom or discontent" , "tiredness" , "Listless boredom" , "to make one list less when connected" , "Boredom in France" .)