Relative knows man I ruined (9)
I believe the answer is:
kinswoman
'relative' is the definition.
(kinswoman is a kind of relative)
'knows man i ruined' is the wordplay.
'ruined' is an anagram indicator.
'knows'+'man'+'i'='knowsmani'
'knowsmani' with letters rearranged gives 'KINSWOMAN'.
(Other definitions for kinswoman that I've seen before include "Relation" , "Female relative" , "Female family member" , "one of the family!" .)