Latest fashion for sailors (6)
I believe the answer is:
modern
'latest' is the definition.
('modern' can be similar in meaning to 'latest')
'fashion for sailors' is the wordplay.
'fashion' becomes 'mode' ('mode' can be a synonym of 'fashion'**).
'for' means one lot of letters go next to another.
'sailors' becomes 'rn' (abbreviation for Royal Navy).
'mode'+'rn'='MODERN'
(Other definitions for modern that I've seen before include "Activity of 18 ac" , "Recent, up to date" , "'Contemporary, up-to-date (6)'" , "In history, the period or era since the Middle Ages" , "Of the present time or current fashion" .)