He goes to work at last (7)
I believe the answer is:
cobbler
'he' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'goes to work at last' is the wordplay.
'goes' becomes 'r' (I can't justify this - if you can you should give a lot more credence to this answer).
'to' means one lot of letters go next to another (I've seen this in other clues).
'work at last' becomes 'cobble' (I've seen this before).
'r' put after 'cobble' is 'COBBLER'.
(Other definitions for cobbler that I've seen before include "Shoemaker and repairer" , "one getting down to work at last?" , "'Let the ....... stick to hid last'" , "Iced drink - fruit pie with a crunchy topping" , "Shoe-repairer" .)