Stories, say, possibly about the navy (5)
I believe the answer is:
yarns
'stories' is the definition.
('yarn' can be a synonym of 'story')
'say possibly about the navy' is the wordplay.
'possibly' indicates an anagram.
'about' means one lot of letters goes inside another.
'the navy' becomes 'RN' (abbreviation for Royal Navy).
'say' is an anagram of 'yas'.
'yas' going around 'rn' is 'YARNS'.
(Other definitions for yarns that I've seen before include "Tales; threads" , "Anecdotes" , "Stories, threads" , "Wools or stories" , "rambling stories" .)