Mean woman in bad temper, blowing top? (7)
I believe the answer is:
average
'mean' is the definition.
('average' can be a synonym of 'mean')
'woman in bad temper blowing top?' is the wordplay.
'woman' becomes 'vera' (a woman's name**).
'in' means one lot of letters goes inside another.
'bad temper' becomes 'rage'.
'blowing top?' means to remove the first letter.
'rage' with its initial letter taken away is 'age'.
'vera' put within 'age' is 'AVERAGE'.
(Other definitions for average that I've seen before include "'Medium, middling (7)'" , "Mean - everyday" , "mean maybe" , "Normal in arithmetic way" , "It may be mean" .)