Garden of trees? Lily taking in mine heading for terrace (9)
I believe the answer is:
arboretum
'garden of trees?' is the definition.
(I've seen this before)
'lily taking in mine heading for terrace' is the wordplay.
'lily' becomes 'arum' (a type of lily).
'taking in' means one lot of letters goes inside another.
'mine' becomes 'bore' (as in boring or mining into something).
'heading for' indicates taking the first letters.
The first letter of 'terrace' is 't'.
'bore'+'t'='boret'
'arum' going around 'boret' is 'ARBORETUM'.
(Other definitions for arboretum that I've seen before include "Botanic garden of trees" , "Garden where trees and shrubs are cultivated" , "there's high growth" , "Collection of elders, say" , "area with great growth" .)