Deep area at the side of ship (5)
I believe the answer is:
abyss
'deep' is the definition.
(thesaurus)
'area at the side of ship' is the wordplay.
I cannot quite see how this works, but
'area' could be 'a' (maths abbreviation) and 'a' is found in the answer.
'side' could be 'by' (synonyms) and 'by' is found within the answer.
'ship' could be 'ss' (prefix in ship names eg SS Great Britain) and 'ss' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for abyss that I've seen before include "ocean depth" , "Very deep gorge" , "crevasse" , "Primal chaos" , "Seemingly bottomless chasm" .)