Flier has a sash in the Royal Navy (5)
I believe the answer is:
robin
'flier' is the definition.
(robin is a kind of birdanimal)
'a sash in the royal navy' is the wordplay.
'a sash' becomes 'obi' (type of Japanese sash or belt).
'in the' indicates putting letters inside.
'royal navy' becomes 'RN' (abbreviation for Royal Navy).
'obi' inserted into 'rn' is 'ROBIN'.
'has' is the link.
(Other definitions for robin that I've seen before include "Seasonal bird" , "Friendly winter bird" , "flier" , "Garden bird" , "good fellow in the D [DREAM]" .)