Amuses Mark and Leslie! (7)
I believe the answer is:
tickles
'amuses' is the definition.
(I've seen this before)
'mark and leslie' is the wordplay.
'mark' becomes 'tick' (I've seen this before).
'and' means one lot of letters go next to another.
'leslie' becomes 'les'.
'tick'+'les'='TICKLES'
(Other definitions for tickles that I've seen before include "Light touches that cause laughter" , "Excites" , "Soft touches" , "Amuses" .)