Tim and Megan's involvement shows attractive quality (9)
I believe the answer is:
magnetism
'attractive quality' is the definition.
(I've seen this in another clue)
'tim and megan's involvement' is the wordplay.
'and' is a charade indicator (letters next to each other).
'involvement' is an anagram indicator.
'tim' after 'megans' is 'meganstim'.
'meganstim' anagrammed gives 'MAGNETISM'.
'shows' is the link.
(Other definitions for magnetism that I've seen before include "Drawing power" , "Attraction" , "Charisma" , "Attractive force" .)