Normal mature woman inside (7)
I believe the answer is:
average
'normal' is the definition.
('average' can be a synonym of 'normal')
'mature woman inside' is the wordplay.
'mature' becomes 'age' ('age' can be a synonym of 'mature').
'woman' becomes 'vera' (a woman's name**).
'inside' means one lot of letters goes inside another.
'age' enclosing 'vera' is 'AVERAGE'.
(Other definitions for average that I've seen before include "Arithmetical mean" , "Arithmetically ordinary?" , "Mean - norm" , "Mean - ordinary" , "'Medium, middling (7)'" .)