The lout, when he'd been caught entering, became violent (6,3)
I believe the answer is:
lashed out
'the lout' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'he'd been caught entering became violent' is the wordplay.
I cannot really understand how this works, but
'he'd' could be 'hed' and 'hed' is found within the answer.
'caught' could be 'out' and 'out' is present in the answer.
The remaining letters 'las' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'when' is the link.
Can you help me to learn more?
(Other definitions for lashed out that I've seen before include "Spent extravagantly" , "Attacked with words or blows - or whip?" , "Spent money freely" , "Was open-handed - or used one's fists?" , "struck at random" .)