Book penned by naval man, actually (7)
I believe the answer is:
almanac
'book' is the definition.
(almanac is a kind of book)
'penned by naval man actually' is the wordplay.
'penned by' says the answer is hidden in the clue.
'ALMANAC' is hidden within 'naval man actually'.
(Other definitions for almanac that I've seen before include "Register" , "periodic publication" , "Annual publication, Old Moore's perhaps" , "Annual calendar or handbook" , "Year book with astronomical events, tides etc" .)