Cloudy and strangely unable to start raining (7)
I believe the answer is:
nebular
'cloudy' is the definition.
('nebular' can be similar in meaning to 'cloudy')
'strangely unable to start raining' is the wordplay.
'strangely' indicates an anagram.
'to' is a charade indicator (letters next to each other).
'start' says to take the initial letters.
The first letter of 'raining' is 'r'.
'unable' anagrammed gives 'nebula'.
'nebula'+'r'='NEBULAR'
'and' is the link.
(Other definitions for nebular that I've seen before include "Relating to astronomical cloud" , "Cloudlike" , "Hazy and formless" , "Like a cloud (in space)" , "Misty" .)