Old sailor wants dosage adjusted (3,3)
I believe the answer is:
sea dog
'old sailor' is the definition.
(I've seen this before)
'dosage adjusted' is the wordplay.
'adjusted' indicates anagramming the letters.
'dosage' anagrammed gives 'SEA-DOG'.
'wants' is the link.
(Other definitions for sea dog that I've seen before include "Experienced sailor (colloq.)" , "mythical creature" , "An old sailor of canine origin" , "Old or experienced sailor" , "Experienced mariner" .)