Frightful rain in the country (4)
I believe the answer is:
iran
'the country' is the definition.
(Iran is a country)
'frightful rain' is the wordplay.
'frightful' is an anagram indicator (a frightful spelling).
'rain' is an anagram of 'IRAN'.
'in' acts as a link.
(Other definitions for iran that I've seen before include "bombless state" , "It used to be Persia" , "Country where the official language is Farsi" , "Modern name for Persia" , "Country of western Asia" .)