Upon parting, it may be said out of love (5)
I believe the answer is:
adios
'upon parting it' is the definition.
I can't judge whether this definition defines the answer.
'may be said out of love' is the wordplay.
'may be' indicates an anagram.
'out of' indicates putting letters inside (some letters on the outside of others).
'love' becomes 'o' (love means zero in tennis).
'said' is an anagram of 'adis'.
'adis' enclosing 'o' is 'ADIOS'.
Can you help me to learn more?
(Other definitions for adios that I've seen before include "See you in Ibiza" , "Adieu, arrivederci" , "Bye!" , "Good-bye (Sp.)" , "Bye-bye (amigo)" .)