Returning train contains drawn-out area for tree with showy flowers (8)
I believe the answer is:
magnolia
'tree with showy flowers' is the definition.
(I've seen this before)
'returning train contains drawn-out area' is the wordplay.
'returning' says the letters should be written in reverse.
'train' becomes 'aim' (synonyms).
'contains' means one lot of letters goes inside another.
'drawn-out' becomes 'long' (drawn-out can mean unnecessarily long).
'area' becomes 'a' (maths abbreviation).
'long'+'a'='longa'
'aim' going around 'longa' is 'ailongam'.
'ailongam' backwards is 'MAGNOLIA'.
'for' acts as a link.
(Other definitions for magnolia that I've seen before include "Tree with showy flowers" , "Creamy white, shrub" , "Fragrant bloom might strangely gain loam" , "Fragrant blooms might strangely gain loam" , "bush" .)