Area near steamship that's very deep (5)
I believe the answer is:
abyss
'that's very deep' is the definition.
'area near steamship' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'near' becomes 'by' (I've seen this in other clues).
'steamship' becomes 'ss'.
'a'+'by'+'ss'='ABYSS'
(Other definitions for abyss that I've seen before include "Deep hole, seems bottomless" , "Bottomless gulf" , "Seemingly bottomless chasm" , "Deep gulf" , "deep depression" .)