The middle age of a goddess (4)
I believe the answer is:
hera
'a goddess' is the definition.
(thesaurus)
'the middle age' is the wordplay.
'middle' indicates the central letters.
'age' becomes 'era' (I've seen this before**).
The central letter of 'the' is 'h'.
'h'+'era'='HERA'
'of' acts as a link.
(Other definitions for hera that I've seen before include "Wife of Jupiter" , "female Greek deity" , "Sister and wife of 18" , "Zeus's wife and sister" , "Divinity" .)