Obelisk built by Greek character in very little time (8)
I believe the answer is:
monument
'obelisk' is the definition.
(thesaurus)
'greek character in very little time' is the wordplay.
'greek character' becomes 'nu' (letter from the Greek alphabet).
'in' means one lot of letters goes inside another.
'very little time' becomes 'moment' (I can't justify this - if you can you should believe this answer much more).
'nu' going within 'moment' is 'MONUMENT'.
'built by' is the link.
Can you help me to learn more?
(Other definitions for monument that I've seen before include "Lasting record" , "cairn" , "Commemorative statue, building etc." , "London tube station" , "Commemorative structure" .)