Charts pirate had at sea (3,6)
I believe the answer is:
hit parade
'charts' is the definition.
(list of top songs in the music charts)
'pirate had at sea' is the wordplay.
'at sea' indicates anagramming the letters.
'pirate'+'had'='piratehad'
'piratehad' is an anagram of 'HIT PARADE'.
(Other definitions for hit parade that I've seen before include "Top-selling numbers" , "Selling CDs" , "Those once charting" , "list of winners" , "Pop charts" .)