Build complex with new capital (6)
I believe the answer is:
dublin
'capital' is the definition.
(Dublin is an example)
'build complex with new' is the wordplay.
'complex with' indicates anagramming the letters.
'new' becomes 'n'.
'build' with its letters anagrammed with 'n' makes 'DUBLIN'.
(Other definitions for dublin that I've seen before include "Ulysses city (Joyce)" , "European city" , "Capital of Eire" , "City of 1 across" , "Irish capital city" .)