The old man, like myself, had so healthy an upbringing (10)
I believe the answer is:
methuselah
'the old man' is the definition.
(I've seen this before)
'myself had so healthy an upbringing' is the wordplay.
'myself' becomes 'me'.
'had' says to put letters next to each other.
'so' becomes 'thus' (synonyms).
'healthy' becomes 'hale' (hale can mean fit and healthy).
'an upbringing' shows that the letters should be reversed in order.
'hale' back-to-front is 'elah'.
'me'+'thus'+'elah'='METHUSELAH'
'like' is the link.
(Other definitions for methuselah that I've seen before include "One very old" , "Old man of the Bible" , "Old Testament patriarch (very old when he died!)" , "able to hold a lot of drink" , "He lived 969 years (Gen.)" .)