Six-footer in ocean trip (3)
I believe the answer is:
ant
'six-footer' is the definition.
(ants have six feet)
'in ocean trip' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ANT' is hidden in the letters of 'ocean trip'.
(Other definitions for ant that I've seen before include "One working hard" , "Termite" , "The insect lives in a social colony" , "Colonial insect?" , "Hill-dweller" .)