Sailor in pit finding Davy Jones's locker? (6)
I believe the answer is:
seabed
'davy jones's locker?' is the definition.
('seabed' can be a synonym of 'davy jones's locker')
'sailor in pit' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'in' is an insertion indicator.
'pit' becomes 'seed' ('pit' is a US term for the stone of a fruit).
'ab' put within 'seed' is 'SEABED'.
'finding' acts as a link.
(Other definitions for seabed that I've seen before include "Debase (anag)" , "marine base" , "Davy Jones's locker" , "Bottom of the ocean" , "The ocean floor, not for sleeping" .)