Strong cat, lithe, jumping (8)
I believe the answer is:
athletic
'strong' is the definition.
(I've seen this before)
'cat lithe jumping' is the wordplay.
'jumping' indicates an anagram.
'cat'+'lithe'='catlithe'
'catlithe' is an anagram of 'ATHLETIC'.
(Other definitions for athletic that I've seen before include "Wigan, for example" , "With a strong and well proportioned body" , "Fit and sporty" , "Lithe act (anag)" , "Sporty, able-bodied" .)