Cats lie around, flexible (7)
I believe the answer is:
elastic
'flexible' is the definition.
(I know that flexible can be written as elastic)
'cats lie around' is the wordplay.
'around' is an anagram indicator.
'cats'+'lie'='catslie'
'catslie' anagrammed gives 'ELASTIC'.
(Other definitions for elastic that I've seen before include "Ductile" , "Flexible, adaptable" , "Flexible rubbery strip" , "Able to give a bit" , "Springy, like a rubber band" .)