Song and dance on navy deck (5)
I believe the answer is:
adorn
'deck' is the definition.
(I've seen this before)
'song and dance on navy' is the wordplay.
'song and dance' becomes 'ado' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'navy' becomes 'RN' (abbreviation for Royal Navy).
'ado'+'rn'='ADORN'
(Other definitions for adorn that I've seen before include "Improve appearance" , "Bedeck" , "Make more attractive" , "Beautify - decorate - enhance" , "Deck" .)