Child is bad then well (9)
I believe the answer is:
offspring
'child' is the definition.
(thesaurus)
'bad then well' is the wordplay.
'bad' becomes 'off' (I've seen this before).
'then' says to put letters next to each other.
'well' becomes 'spring' (I've seen this before**).
'off'+'spring'='OFFSPRING'
'is' acts as a link.
(Other definitions for offspring that I've seen before include "Children, issue" , "seed" , "Young" , "Kids" , "Result" .)