Spills catsup and behaves badly (4,2)
I believe the answer is:
acts up
'behaves badly' is the definition.
(acting up is a kind of behaving badly)
'spills catsup' is the wordplay.
'spills' indicates an anagram.
'catsup' with letters rearranged gives 'ACTS UP'.
'and' acts as a link.
(Other definitions for acts up that I've seen before include "Misbehaves badly" , "Carries on" , "Causes trouble or misbehaves" , "Malfunctions" , "Behaves in a troublesome way" .)