Grand complex surrounds European area of cultivation (6)
I believe the answer is:
garden
'area of cultivation' is the definition.
(area where plants are cultivated)
'grand complex surrounds european' is the wordplay.
'complex' indicates an anagram.
'surrounds' indicates putting letters inside.
'european' becomes 'e' (abbreviation e.g. EU).
'grand' anagrammed gives 'gardn'.
'gardn' placed around 'e' is 'GARDEN'.
(Other definitions for garden that I've seen before include "Cultivate a plot" , "Danger in Eden?" , "Ranged (anag.)" , "Danger (anag.)" , "park" .)