Meeting rearranged when it's pouring (7)
I believe the answer is:
teeming
'it's pouring' is the definition.
(I've seen this before)
'meeting rearranged' is the wordplay.
'rearranged' indicates anagramming the letters.
'meeting' anagrammed gives 'TEEMING'.
'when' is the link.
(Other definitions for teeming that I've seen before include "Pouring - abounding" , "Alive" , "Full of, abounding in" , "Full of people" , "Abundant" .)