Plus, Dad is confused (3)
I believe the answer is:
add
'plus' is the definition.
(thesaurus)
'dad is confused' is the wordplay.
'is confused' indicates an anagram.
'dad' is an anagram of 'ADD'.
(Other definitions for add that I've seen before include "Sum up; say further" , "Total; put together" , "Contribute" , "Go further" , "Augment" .)