Joking around, with sons instead of daughters, is just touching (7)
I believe the answer is:
kissing
'is just touching' is the definition.
(I've seen this before)
'joking around with sons instead of' is the wordplay.
'around' says to take the centre.
'with' says to put letters next to each other.
'sons' becomes 'ss' (genealogical abbreviation for son written twice).
'instead of' becomes 'ing' (I can't justify this - if you can you should believe this answer much more).
The centre of 'joking' is 'ki'.
'ki'+'ss'+'ing'='KISSING'
'daughters' is the link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for kissing that I've seen before include "Osculation" , "Caressing with lips" , "delivering smack" , "Osculating" , "Gently touching" .)