Recent arrival discovered domes C Wren designed (8)
I believe the answer is:
newcomer
'recent arrival' is the definition.
(I've seen this before)
'discovered domes c wren designed' is the wordplay.
'discovered' indicates the central letters (dis-covered - outer letters removed).
'designed' indicates anagramming the letters (designed with the letters).
The central letters of 'domes' are 'ome'.
'ome'+'c'+'wren'='omecwren'
'omecwren' anagrammed gives 'NEWCOMER'.
(Other definitions for newcomer that I've seen before include "Late arrival" , "2 arrival" , "Fresh arrival" , "Starter" , "He has just arrived or started" .)