I attempt to follow gang for criminal activity (8)
I believe the answer is:
banditry
'criminal activity' is the definition.
(I've seen this before)
'i attempt to follow gang' is the wordplay.
'attempt to' becomes 'try' (I've seen this in other clues).
'follow' means one lot of letters go next to another.
'gang' becomes 'band' (both can mean a group of people).
'i'+'try'='itry'
'itry' after 'band' is 'BANDITRY'.
'for' acts as a link.
(Other definitions for banditry that I've seen before include "Brigandage" , "Criminal activity" , "Plundering in gangs" , "Activity of armed robbers" , "Activity of violent robbers" .)