A qualification of use in navigation (6)
I believe the answer is:
degree
'a qualification' is the definition.
(university qualification)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for degree that I've seen before include "The measure of a university award?" , "displayed by small elevated circle" , "Graduate's qualification" , "Fraction of a minute" , "Educational qualification" .)