Area near ship in ocean depths (5)
I believe the answer is:
abyss
'ocean depths' is the definition.
(thesaurus)
'area near ship' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'near' becomes 'by' (near means close by).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'a'+'by'+'ss'='ABYSS'
'in' acts as a link.
(Other definitions for abyss that I've seen before include "Deep pit" , "Very deep gorge" , "Bottomless gulf" , "depths of sea" , "Deep hole, seems bottomless" .)