Behold new dress in metropolis (6)
I believe the answer is:
london
'metropolis' is the definition.
(I know that London is a metropolis)
'behold new dress' is the wordplay.
'behold' becomes 'lo' (archaic exclamation meaning 'look!').
'new' becomes 'n' (abbreviation as in New Testament NT).
'dress' becomes 'don' (donning is a kind of dressing).
'lo'+'n'+'don'='LONDON'
'in' acts as a link.
(Other definitions for london that I've seen before include "source of this paper" , "Home of Cockney" , "UK's capital" , "- Clay; - pride; - plane" , "City of the Cockneys" .)