Sparks' latest record is hard work (4)
I believe the answer is:
slog
'is hard work' is the definition.
(a slog is a long or difficult task)
'sparks' latest record' is the wordplay.
'latest' indicates one should take the final letters.
'record' becomes 'log' (logging is a kind of recording).
The last letter of 'sparks' is 's'.
's'+'log'='SLOG'
(Other definitions for slog that I've seen before include "Very tiring work" , "big hit" , "Hit hard - hard trek" , "Work doggedly" , "Work (or walk) involving great effort" .)