Lot of publicity before unhappy oceanic homecoming (10)
I believe the answer is:
splashdown
'oceanic homecoming' is the definition.
(an aircraft landing in the sea)
'lot of publicity before unhappy' is the wordplay.
'lot of publicity' becomes 'splash' (as in a newspaper splash).
'before' is a charade indicator (letters next to each other).
'unhappy' becomes 'down' (I've seen this before).
'splash'+'down'='SPLASHDOWN'
(Other definitions for splashdown that I've seen before include "return of spacecraft" , "Spacecraft's landing at sea" , "Landing of spacecraft on water" , "A drop in the ocean" , "End of mission" .)