Singer prepared to admit defeat (6)
I believe the answer is:
resign
'admit defeat' is the definition.
(I've seen this before)
'singer prepared' is the wordplay.
'prepared' indicates an anagram.
'singer' with letters rearranged gives 'RESIGN'.
'to' is the link.
(Other definitions for resign that I've seen before include "Give up office" , "Hand in one's notice" , "withdraw" , "Stand down" , "Step down" .)