Sailor’s aged, so suffers (3,3)
I believe the answer is:
sea dog
'sailor's' is the definition.
(sea dog is a kind of sailor)
'aged so suffers' is the wordplay.
'suffers' is an anagram indicator.
'aged'+'so'='agedso'
'agedso' anagrammed gives 'SEA-DOG'.
(Other definitions for sea dog that I've seen before include "An old sailor of canine origin" , "Experienced mariner" , "Ancient Mariner" , "Old or experienced sailor" , "Old tar" .)