Drug the Spanish boy found in German city area (10)
I believe the answer is:
belladonna
'drug' is the definition.
(I've seen this before)
'the spanish boy found in german city area' is the wordplay.
'the spanish' becomes 'el' ('the' in Spanish).
'boy' becomes 'lad' (informal term for boy).
'found in' indicates putting letters inside.
'german city' becomes 'bonn' (city in Germany).
'area' becomes 'a' (maths abbreviation).
'el'+'lad'='ellad'
'ellad' inserted inside 'bonn' is 'belladonn'.
'belladonn'+'a'='BELLADONNA'
(Other definitions for belladonna that I've seen before include "Boy in Lebanon destroyed" , "brought a sparkle to the eye" , "Deadly nightshade or atropine" , "Could it poison" , "drug supplier" .)