Juggling act -- lithe, fit and active (8)
I believe the answer is:
athletic
'fit and active' is the definition.
(I've seen this before)
'juggling act lithe' is the wordplay.
'juggling' indicates an anagram (I've seen this in other clues).
'act'+'lithe'='actlithe'
'actlithe' with letters rearranged gives 'ATHLETIC'.
(Other definitions for athletic that I've seen before include "Good at running and jumping" , "Sporting, vigorous" , "With a strong and well proportioned body" , "Physically fit, strong and active" , "Active, sporty" .)