Station Ted back outside the Post Office (5)
I believe the answer is:
depot
'station' is the definition.
(I know that depot is a type of station)
'ted back outside the post office' is the wordplay.
'back' says the letters should be written backwards.
'outside' means one lot of letters goes inside another (some letters go outside others).
'the post office' becomes 'po' (abbreviation).
'ted' back-to-front is 'det'.
'det' enclosing 'po' is 'DEPOT'.
(Other definitions for depot that I've seen before include "Place for storing or despatching goods" , "Wherein bus drivers" , "Supply base" , "storeroom" , "Store for large quantities" .)