Cats lie around, being flexible (7)
I believe the answer is:
elastic
'being flexible' is the definition.
(associated in meaning)
'cats lie around' is the wordplay.
'around' indicates anagramming the letters.
'cats'+'lie'='catslie'
'catslie' with letters rearranged gives 'ELASTIC'.
(Other definitions for elastic that I've seen before include "Pliable" , "Stretch material" , "Flexible rubber strip" , "Castile (anag)" , "Resilient" .)