He scores fast, but seems to make hard work of it (7)
I believe the answer is:
slogger
'he scores fast but seems to' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'hard work of it' is the wordplay.
'hard work' becomes 'slog' (a slog is a long or difficult task).
'of it' becomes 'ger' (I can't justify this - if you can you should give a lot more credence to this answer).
'slog'+'ger'='SLOGGER'
'make' acts as a link.
Can you help me to learn more?
(Another definition for slogger that I've seen is " one who toils".)