Yearbook hidden by naval man, a commodore (7)
I believe the answer is:
almanac
'yearbook' is the definition.
(I know that almanac is a type of yearbook)
'hidden by naval man a commodore' is the wordplay.
'hidden' indicates the answer is hidden within the clue.
'ALMANAC' can be found hidden inside 'by naval man a commodore'.
(Other definitions for almanac that I've seen before include "Statistical annual" , "Annual calendar or handbook" , "Year book with astronomical events, tides etc" , "Calendar with detailed information" , "Sailor's or farmer's calendar" .)