Instructs processions (6)
I believe the answer is:
trains
I believe this clue is a double definition.
'instructs' is the first definition.
(training is a kind of instructing)
'processions' is the second definition.
(train is a kind of procession)
(Other definitions for trains that I've seen before include "Aims; coaches" , "Sets of railway cars" , "Pieces of cloth trailing from the backs of gowns" , "Public transport vehicles with carriages" , "Prepares by practice for performance" .)