Three-dimensional scene showing one love in the play (7)
I believe the answer is:
diorama
'three-dimensional scene' is the definition.
(a 3D model)
'one love in the play' is the wordplay.
'one' becomes 'i' (Roman numeral).
'love' becomes 'o' (love means zero in tennis).
'in the' means one lot of letters goes inside another.
'play' becomes 'drama' (synonyms).
'i'+'o'='io'
'io' placed into 'drama' is 'DIORAMA'.
'showing' acts as a link.
(Other definitions for diorama that I've seen before include "Model representing a scene with three-dimensional figures" , "Scene with models" , "A little set" , "3-D model representing a scene" , "Miniature 3-D scene -- or a maid (anag)" .)