Everyman 'so robust': on the contrary, he reached age of 969! (10)
I believe the answer is:
methuselah
'he reached age of 969' is the definition.
(bible figure notable for long age)
'everyman so robust on the contrary' is the wordplay.
'everyman' becomes 'me' (where 'Everyman' is the setter of the crossword).
'so' becomes 'thus' (synonyms).
'robust' becomes 'hale' (in good health).
'on the contrary' says the letters should be written in reverse (letters in the opposite or contrary direction).
'hale' backwards is 'elah'.
'me'+'thus'+'elah'='METHUSELAH'
(Other definitions for methuselah that I've seen before include "Large wine bottle -- biblical patriarch" , "I'm an old man" , "so much champagne" , "a lot of bottle" , "Old Testament patriarch (very old when he died!)" .)