Downpour: worry, missing outsiders, in shelter (7)
I believe the answer is:
torrent
'downpour' is the definition.
('torrent' can be a synonym of 'downpour')
'missing outsiders in shelter' is the wordplay.
'missing' becomes 'torre' (I can't explain this - if you can you should give a lot more credence to this answer).
'outsiders in' means to remove the middle letters.
'shelter' becomes 'nest' (I've seen this in other clues).
'nest' with its middle taken out is 'nt'.
'torre'+'nt'='TORRENT'
'worry' acts as a link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for torrent that I've seen before include "Overwhelming outpouring" , "Rush of water" , "Great stream" , "Inundation" , "Heavy rain" .)