Teaches half-wits to get out of the rain (6)
I believe the answer is:
trains
'teaches half-wits' is the definition.
'trains' can be an answer for 'teaches' (training is a kind of teaching). I'm not certain of the 'half-wits' bit.
'get out of the rain' is the wordplay.
'get' becomes 'ts' (I can't justify this - if you can you should believe this answer much more).
'out of' indicates putting letters inside.
'ts' placed around 'rain' is 'TRAINS'.
'to' is the link.
Can you help me to learn more?
(Other definitions for trains that I've seen before include "Prepares for competition" , "schools" , "Locomotive-drawn rail cars" , "Works out" , "Pieces of cloth trailing from the backs of gowns" .)