Work hard to produce singer's first record (4)
I believe the answer is:
slog
'work hard' is the definition.
(slog can mean to work very hard)
'singer's first record' is the wordplay.
'singer's first' becomes 's' (1st letter of 'singer').
'record' becomes 'log' (log is a kind of record).
's'+'log'='SLOG'
'to produce' acts as a link.
(Other definitions for slog that I've seen before include "Exhausting task" , "Walk hard carrying logs?" , "Hit out without style" , "Hit hard - hard trek" , "almighty wallop" .)