Fuss with the navy on deck (5)
I believe the answer is:
adorn
'deck' is the definition.
(I've seen this in another clue)
'fuss with the navy' is the wordplay.
'fuss' becomes 'ado' (synonyms).
'with' is a charade indicator (letters next to each other).
'the navy' becomes 'RN' (Royal Navy).
'ado'+'rn'='ADORN'
'on' is the link.
(Other definitions for adorn that I've seen before include "Embellish, decorate" , "Beautify - decorate - enhance" , "Make more attractive" , "Bedeck" , "Improve appearance" .)