Once again left an account (6)
I believe the answer is:
report
'an account' is the definition.
(I know that account can be written as report)
'once again left' is the wordplay.
'once again' becomes 're' (prefix in verbs).
'left' becomes 'port' (left side of a ship - opposite of starboard).
're'+'port'='REPORT'
(Other definitions for report that I've seen before include "Teacher's assessment" , "Formal account of a matter" , "Article" , "Gunfire noise; rumour" , "Account; loud noise" .)