Most annoyed about a little bit of rainy weather (5)
I believe the answer is:
storm
'weather' is the definition.
(I have seen 'Violent weather' mean 'storm' so perhaps 'weather' could also mean 'storm')
'most annoyed about a little bit of rainy' is the wordplay.
'annoyed' indicates an anagram.
'about' means one lot of letters goes inside another.
'a little bit of' indicates taking the first letters (I've seen 'little bits of' mean this).
The first letter of 'rainy' is 'r'.
'most' anagrammed gives 'stom'.
'stom' going around 'r' is 'STORM'.
(Other definitions for storm that I've seen before include "Force 10 blow" , "- drain; - cloud" , "Big fuss" , "Awful blow" , "Gale, tempest" .)