Navy fashion started fresh (6)
I believe the answer is:
modern
'fresh' is the definition.
(I've seen this in another clue)
'navy fashion started' is the wordplay.
'navy' becomes 'RN' (abbreviation for Royal Navy).
'fashion' becomes 'mode' (synonyms).
'started' says to put letters next to each other.
'rn' put after 'mode' is 'MODERN'.
(Other definitions for modern that I've seen before include "Recent, up to date" , "See 11" , "In history, the period or era since the Middle Ages" , "'Contemporary, up-to-the-minute (6)'" , "Activity of 18 ac" .)