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' is an anagram of 'RESIGN'.
'to' acts as a link.
(Other definitions for resign that I've seen before include "Give up office" , "Hand in one's notice" , "withdraw" , "Stand down" , "Step down" .)