Unfashionable person criticising training (6-7)
I believe the answer is:
square-bashing
'training' is the definition.
(square-bashing is a kind of training)
'unfashionable person criticising' is the wordplay.
I cannot quite see how this works, but
'person' could be 'reb' (Reb is an example) and 'reb' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for square-bashing that I've seen before include "Parade-ground drill" , "Parade ground drill" , "Military drill (informal)" .)