Small picture shows day when teachers get more training (5)
I believe the answer is:
inset
This clue is a double definition.
'small picture' is the first definition.
(I've seen this before)
'day when teachers get more training' is the second definition.
(in-service training day)
'shows' acts as a link.
(Other definitions for inset that I've seen before include "Synagogue singer" , "Piece let into a garment" , "Small piece inserted" , "lesser feature" , "Piece introduced" .)