Give up job as lousy singer (6)
I believe the answer is:
resign
'give up job' is the definition.
(I've seen this before)
'lousy singer' is the wordplay.
'lousy' indicates anagramming the letters.
'singer' with letters rearranged gives 'RESIGN'.
'as' is the link.
(Other definitions for resign that I've seen before include "Give up office" , "surrender" , "Step down" , "Turn over" , "Give up one's post" .)