It's touching when leader becomes married in absentia (7)
I believe the answer is:
kissing
'leader becomes married in absentia' is the definition.
I can't tell whether this definition defines the answer.
'it's touching when' is the wordplay.
'it's touching' becomes 'kiss' (kiss is a kind of touching).
'when' becomes 'ing' (I can't justify this - if you can you should believe this answer much more).
'kiss'+'ing'='KISSING'
Can you help me to learn more?
(Other definitions for kissing that I've seen before include "Gently touching" , "Osculation" , "Caressing with lips" , "delivering smack" , "Osculating" .)