Upset at a blue stage presentation (7)
I believe the answer is:
tableau
'presentation' is the definition.
(I have seen 'pictorial presentation' mean 'tableau' so perhaps 'presentation' could also mean 'tableau')
'upset at a blue stage' is the wordplay.
'upset' shows that the letters should be reversed in order.
'stage' indicates anagramming the letters (I've seen 'staged' mean this ('staged' can mean 'organised')).
'at' in reverse letter order is 'ta'.
'a'+'blue'='ablue'
'ablue' is an anagram of 'bleau'.
'ta'+'bleau'='TABLEAU'
(Other definitions for tableau that I've seen before include "Scene of still figures" , "Painting - spectacle" , "Pageant" , "Depiction of a scene by people in costume" , "Group of models representing a scene" .)