Musical I have rejected with thanks (5)
I believe the answer is:
evita
'musical' is the definition.
(I've seen this before)
'i have rejected with thanks' is the wordplay.
'i have' becomes 'ive'.
'rejected' says the letters should be written backwards.
'with' means one lot of letters go next to another.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'ive' backwards is 'evi'.
'evi'+'ta'='EVITA'
(Other definitions for evita that I've seen before include "Eva Peron" , "Stage musical" , "Show" , "Famous musical" , "1978 Lloyd Webber musical" .)