She contradicts Billy (5)
I believe the answer is:
nanny
'billy' is the definition.
(thesaurus)
'she contradicts' is the wordplay.
'she' becomes 'nan'.
'contradicts' becomes 'ny' (I am not sure about this - if you are sure you should believe this answer much more).
'nan'+'ny'='NANNY'
Can you help me to learn more?
(Other definitions for nanny that I've seen before include "Child's nurse or female goat" , "butter" , "Posh child minder or female goat" , "Overprotective government deplored by Thatcher" , "Children's nurse" .)