Wife with peculiar desire (4)
I believe the answer is:
will
'desire' is the definition.
(thesaurus)
'wife with peculiar' is the wordplay.
'wife' becomes 'w'.
'with' is a charade indicator (letters next to each other).
'peculiar' becomes 'ill'.
'w'+'ill'='WILL'
(Other definitions for will that I've seen before include "Intention, desire" , "Shakespeare < 's intention to leave something" , "Record of final wishes and testament" , "Testament or determination" , "Volition" .)