She'll finish up in outer Wembley (5)
I believe the answer is:
wendy
'she'll' is the definition.
I can't tell whether this definition defines the answer.
'finish up in outer wembley' is the wordplay.
'finish up' becomes 'end' (to finish is to come to an end).
'in' means one lot of letters goes inside another.
'outer' means to remove the middle letters.
'wembley' with its middle taken out is 'wy'.
'end' going inside 'wy' is 'WENDY'.
Can you help me to learn more?
(Other definitions for wendy that I've seen before include "Peter Pan's friend" , "Peter's girl-friend" , "Art-loving Sister (TV)" , "31's friend" , "Peter Pan heroine" .)