"A leisure activity that's beyond me," I put in (7)
I believe the answer is:
pastime
'a leisure activity' is the definition.
(I know that pastime is a type of leisure activity)
'beyond me i put in' is the wordplay.
'beyond' becomes 'past' (to go beyond something is to go past it).
'put in' means one lot of letters goes inside another.
'past'+'me'='pastme'
'pastme' enclosing 'i' is 'PASTIME'.
'that's' acts as a link.
(Other definitions for pastime that I've seen before include "Hobby - recreation" , "relaxation" , "Leisure activity" , "Hobby; regular activity" , "doing the crossword, say" .)