New dome constructed by the navy (6)
I believe the answer is:
modern
'new' is the definition.
(synonyms)
'dome constructed by the navy' is the wordplay.
'constructed' indicates anagramming the letters.
'by' is a charade indicator (letters next to each other).
'the navy' becomes 'rn' (abbreviation for Royal Navy).
'dome' anagrammed gives 'mode'.
'mode'+'rn'='MODERN'
(Other definitions for modern that I've seen before include "In history, the period or era since the Middle Ages" , "Recent, up to date" , "Novel" , "Present-day" , "'Contemporary, up-to-date (6)'" .)