Instruct shower after time (5)
I believe the answer is:
train
'instruct' is the definition.
(training is a kind of instructing)
'shower after time' is the wordplay.
'shower' becomes 'rain' (synonyms).
'after' is a charade indicator (letters next to each other).
'time' becomes 't' (abbreviation).
'rain' after 't' is 'TRAIN'.
(Other definitions for train that I've seen before include "Linked carriages" , "Groom" , "become physically fit" , "Teach; followers" , "Work out" .)