Hard rain agitated shrew (8)
I believe the answer is:
harridan
'shrew' is the definition.
(harridan is a kind of shrew)
'hard rain agitated' is the wordplay.
'agitated' indicates anagramming the letters.
'hard'+'rain'='hardrain'
'hardrain' anagrammed gives 'HARRIDAN'.
(Other definitions for harridan that I've seen before include "Bossy old woman" , "Old woman scold" , "Strict and bossy woman" , "Nagger" , "Virago -- rain hard (anag)" .)