A function with navy fellows — time for dressing up (9)
I believe the answer is:
adornment
'dressing up' is the definition.
'a function with navy fellows time' is the wordplay.
'a function' becomes 'ado' (I can't justify this - if you can you should believe this answer much more).
'with' means one lot of letters go next to another.
'navy' becomes 'RN' (Royal Navy).
'fellows' becomes 'men' (fellow can mean a man).
'time' becomes 't' (abbreviation).
'ado'+'rn'+'men'+'t'='ADORNMENT'
'for' is the link.
Can you help me to learn more?
(Other definitions for adornment that I've seen before include "Embellishment" , "form of beautification?" , "Trim" , "Ornamentation" , "decorating" .)