Shoved guards in back, getting chastised (8)
I believe the answer is:
punished
'chastised' is the definition.
('punished' can be similar in meaning to 'chastised')
'shoved guards in back' is the wordplay.
'shoved' becomes 'pushed' (I've seen this before).
'guards' means one lot of letters goes inside another.
'back' shows that the letters should be reversed in order.
'in' back-to-front is 'ni'.
'pushed' placed around 'ni' is 'PUNISHED'.
'getting' acts as a link.
(Other definitions for punished that I've seen before include "Impose a penalty on" , "penalised" , "grounded perhaps?" , "Imposed a penalty" , "Disciplined" .)