Violent behaviour caused by going outside after a drop inside (5)
I believe the answer is:
aggro
'violent behaviour' is the definition.
(I've seen this before)
'going outside after a drop inside' is the wordplay.
'outside' says to hollow out the word (remove centre letters).
'after' means one lot of letters go next to another.
'inside' means to look at the middle letters.
'going' with its centre removed is 'gg'.
The middle of 'drop' is 'ro'.
'gg' after 'a' is 'agg'.
'agg'+'ro'='AGGRO'
'caused by' is the link.
(Other definitions for aggro that I've seen before include "Hostility" , "Aggressive, violent behaviour in short" , "Violence - obstructiveness" , "belligerent behaviour" , "Hostile behaviour" .)