Blood relation ma is known to reform (9)
I believe the answer is:
kinswoman
'blood relation' is the definition.
(I know that kinswoman is a type of blood relation)
'ma is known to reform' is the wordplay.
'to reform' is an anagram indicator (letters in a new form).
'ma'+'is'+'known'='maisknown'
'maisknown' is an anagram of 'KINSWOMAN'.
(Other definitions for kinswoman that I've seen before include "Female family member" , "one of the family!" , "Relation" , "Female relative" .)