"A leisure activity that's beyond me," I put in (7)
I believe the answer is:
pastime
'a leisure activity' is the definition.
(I've seen this before)
'beyond me i put in' is the wordplay.
'beyond' becomes 'past' (I've seen this before).
'put in' is an insertion indicator.
'past'+'me'='pastme'
'pastme' placed around '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" .)