Pasture in impermissible scene (7)
I believe the answer is:
tableau
'scene' is the definition.
(I've seen this before)
'pasture in impermissible' is the wordplay.
'pasture' becomes 'lea' (synonyms).
'in' is an insertion indicator.
'impermissible' becomes 'tabu' (similar in meaning).
'lea' inserted into 'tabu' is 'TABLEAU'.
(Other definitions for tableau that I've seen before include "Motionless figures representing a scene" , "Staged scene" , "still life?" , "- - vivant" , "Figures making a scene" .)