Kind of solver who doesn't obey set of rules? (11)
I believe the answer is:
codebreaker
'kind of solver who doesn't obey' is the definition.
I know nothing about this answer so I can't tell whether this works.
'set of rules?' is the wordplay.
'set' becomes 'code' (I have seen 'Set of rules ' mean 'code' so perhaps 'set' could also mean 'code').
'of rules?' becomes 'breaker' (I can't justify this - if you can you should believe this answer much more).
'code'+'breaker'='CODEBREAKER'
Can you help me to learn more?
(Other definitions for codebreaker that I've seen before include "Bletchley Park worker" , "Person employed as a cracker?" .)