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 am not sure about this - if you are sure you should believe this answer much more).
'to' says to put letters next to each other (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" .)