Never a slave before chancing on the navy (8)

'never a slave' is the definition.
I can't tell whether this defines the answer.

'before chancing on the navy' is the wordplay.
I cannot really see how this works, but
an anagram of 'before' is 'freebo' which is present in the answer.
'navy' could be 'rn' (abbreviation for Royal Navy) and 'rn' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?