Relatives unusually being flexible (9)
I believe the answer is:
versatile
'flexible' is the definition.
(similar in meaning)
'relatives unusually' is the wordplay.
'unusually' indicates an anagram.
'relatives' with letters rearranged gives 'VERSATILE'.
'being' acts as a link.
(Other definitions for versatile that I've seen before include "Capable of many functions" , "Multiskilled" , "Able to adapt" , "Good at adapting oneself" , "Having many uses" .)