It's mean to state how old someone is (7)
I believe the answer is:
average
'it's mean' is the definition.
(synonyms)
'state how old someone is' is the wordplay.
'state' becomes 'aver' (both can mean to declare).
'how old someone is' becomes 'age' (someone's age).
'aver'+'age'='AVERAGE'
'to' is the link.
(Other definitions for average that I've seen before include "Mean - everyday" , "just like any other" , "Mean, so-so" , "Mediocre, commonplace" , "mean maybe" .)