New master having kick about - that's a joke (3,3)
I believe the answer is:
bon mot
'a joke' is the definition.
(thesaurus)
'new master having kick about that's' is the wordplay.
'new' becomes 'n' (abbreviation as in New Testament NT).
'master' becomes 'M' (common abbreviation eg MA, Master of Art).
'having' says to put letters next to each other.
'kick' becomes 'boot' (synonyms).
'about that's' is an insertion indicator.
'n'+'m'='nm'
'nm' put into 'boot' is 'BON MOT'.
(Other definitions for bon mot that I've seen before include "Appropriate word or expression - in France" , "Witty words" , "Witticism" , "Apt or witty remark - in France" , "The right or apposite word - in France" .)