Possible threat of rain that could put some of us in the cold (5)
I believe the answer is:
cloud
'possible threat of rain that could' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'some of us in the cold' is the wordplay.
'some of' suggests taking the first letters (I've seen 'some' mean this).
'in' is an insertion indicator.
'the cold' becomes 'clod' (I can't explain this - if you can you should believe this answer much more).
The initial letter of 'us' is 'u'.
'u' put inside 'clod' is 'CLOUD'.
'put' is the link.
Can you help me to learn more?
(Other definitions for cloud that I've seen before include "''I wandered lonely as a ...'' (Wordsworth)" , "Obscure" , "Condensed air vapour" , "Become less transparent" , "Become gloomy" .)