The bringing about of rain (13)
I believe the answer is:
precipitation
'rain' is the definition.
(I've seen this before)
'the bringing about of' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
'about' could be 're' (regarding) and 're' is present in the answer.
'of' could be 'o' and 'o' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for precipitation that I've seen before include "Rash haste" , "Undue rushing" , "Rain, hail, snow etc" , "Rain, snow, sleet or hail" , "Snow, rain, etc - impetuosity" .)