Singer forced to quit (6)
I believe the answer is:
resign
'quit' is the definition.
(I know that quit can be written as resign)
'singer forced' is the wordplay.
'forced' indicates anagramming the letters.
'singer' with letters rearranged gives 'RESIGN'.
'to' acts as a link.
(Other definitions for resign that I've seen before include "Give up office" , "Step down" , "Give up one's job" , "Stand down" , "surrender" .)