Dispatches boat carrying final piece (5)
I believe the answer is:
sends
'dispatches' is the definition.
(I've seen this in another clue)
'boat carrying final piece' is the wordplay.
'boat' becomes 'SS' (prefix in ship names eg SS Great Britain).
'carrying' indicates putting letters inside.
'final piece' becomes 'end' (I've seen this in another clue).
'ss' going around 'end' is 'SENDS'.
(Other definitions for sends that I've seen before include "Transmits" , "Despatches" , "Causes to go somewhere" .)