Story of some Yank joining the navy (4)
I believe the answer is:
yarn
'story' is the definition.
(synonyms)
'some yank joining the navy' is the wordplay.
'some yank joining' becomes 'yar' (I can't explain this - if you can you should believe this answer much more).
'the navy' becomes 'N' (common abbreviation eg in RN Royal Navy).
'yar'+'n'='YARN'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for yarn that I've seen before include "that'll keep you in stitches?" , "Anecdote" , "Spun thread or wool or tall tale" , "Long involved story" , "A long tale" .)