With this system, the police have a burden to shoulder (6)
I believe the answer is:
method
'with this system the police have a burden to shoulder' is the definition.
'method' can be an answer for 'system' (I've seen this before). I am not certain of the remainder of the definition.
'with this system the police have' is the wordplay.
'with' means one lot of letters goes inside another.
'this system' indicates an anagram (another version or system with the same letters).
'police have' becomes 'mod' (I can't justify this - if you can you should believe this answer much more).
'the' anagrammed gives 'eth'.
'eth' going into 'mod' is 'METHOD'.
Can you help me to learn more?
(Other definitions for method that I've seen before include "Systematic way of doing something" , "rule" , "Way of doing something, perhaps in madness" , "Orderliness; procedure" , "Type of acting" .)