Loudly performed hornpipe for navy? (4)
I believe the answer is:
blue
'navy?' is the definition.
(navy is a kind of blue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for blue that I've seen before include "Oxbridge player" , "Oxbridge sportsman; sad" , "sportsperson" , "The colour of melancholy" , "Down in the mouth" .)