Hail storm that's normal (7)
I believe the answer is:
average
'normal' is the definition.
('average' can be a synonym of 'normal')
'hail storm' is the wordplay.
'hail' becomes 'ave' (I've seen this before).
'storm' becomes 'rage' ('rage' can be a synonym of 'storm').
'ave'+'rage'='AVERAGE'
'that's' acts as a link.
(Other definitions for average that I've seen before include "About normal or usual" , "Mean - everyday" , "Usual - mediocre - mean" , "It's common" , "Normal amount" .)