School temperature drops (5)
I believe the answer is:
train
'school' is the definition.
(training is a kind of schooling)
'temperature drops' is the wordplay.
'temperature' becomes 't' (abbreviation).
'drops' becomes 'rain' (drops of water).
't'+'rain'='TRAIN'
(Other definitions for train that I've seen before include "Tailpiece of bridal gown" , "Coach; attendants" , "Body of followers, retinue" , "Learn a skill etc. through practice" , "Locomotive plus carriages" .)