Unrealistic dream of such as Big Ben area (7)
I believe the answer is:
chimera
'unrealistic dream of' is the definition.
The definition suggests a singular noun which matches the answer.
'big ben area' is the wordplay.
'big ben' becomes 'chimer' (Big Ben is a famous bell - bells chime).
'area' becomes 'a' (maths abbreviation).
'chimer'+'a'='CHIMERA'
'such as' acts as a link.
Can you help me to learn more?
(Other definitions for chimera that I've seen before include "Mythical monster, part lion, goat and serpent" , "Each rim (anag) - foolish fancy" , "Mythological animal; something illusory" , "Wild or impossible idea" , "fabulous creature" .)