Give up crime resolving this aggro with thieves' leader (2,8)
I believe the answer is:
go straight
'up crime resolving this aggro with thieves' leader' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'give' is the wordplay.
I cannot really understand how this works, but
'give' could be 'go' ('go' can be a synonym of 'give') and 'go' is present in the answer.
The remaining letters 'straight' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for go straight that I've seen before include "Turn to an honest life" , "Cease criminality" , "Renounce all criminal activities" .)