Claimed to be mistreated: one has a point! (7)
I believe the answer is:
decimal
'one has a point' is the definition.
(as in a decimal point)
'claimed to be mistreated' is the wordplay.
'to be mistreated' indicates an anagram.
'claimed' is an anagram of 'DECIMAL'.
(Other definitions for decimal that I've seen before include "Relating to ten" , "Medical (anag.)" , "Claimed (anag) - a point" , "A point in maths" , "of Number Ten" .)