Players get disturbed about old treatment for internal problem (6,3)
I believe the answer is:
inside job
'players get disturbed about old treatment' is the definition.
I can't judge whether this defines the answer.
'internal problem' is the wordplay.
'internal' becomes 'inside' (associated in meaning).
'problem' becomes 'job' (synonyms).
'inside'+'job'='INSIDE JOB'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for inside job that I've seen before include "crime of disloyalty" , "Staff-colluding crime" , "doublecrossing crime" , "Sort of crime" , "Crime with collusion" .)