Penguin, say, right behind blue ship at sea (9)
I believe the answer is:
publisher
'penguin say' is the definition.
(I know that Penguin Books is a publisher)
'right behind blue ship at sea' is the wordplay.
'right' becomes 'r' (abbreviation).
'behind' means one lot of letters go next to another.
'at sea' indicates an anagram.
'blue'+'ship'='blueship'
'blueship' is an anagram of 'publishe'.
'r' put after 'publishe' is 'PUBLISHER'.
(Other definitions for publisher that I've seen before include "bookmaker!" , "damned by a duke" , "Eg Jonathan Cape or Hamish Hamilton" , "House of books" , "Man with many titles" .)