Set part of drama on rails (7)
I believe the answer is:
scenery
'set' is the definition.
(scenery is a kind of set)
'part of drama on rails' is the wordplay.
'part of drama' becomes 'scene' ('scene' is part of 'drama').
'on rails' becomes 'ry' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'scene'+'ry'='SCENERY'
Can you help me to learn more?
(Other definitions for scenery that I've seen before include "On-stage background" , "Structures of a stage set" , "Theatrical background" , "sight" , "flats" .)