One who worked like a horse? (6)
I believe the answer is:
trojan
'one who worked' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a horse?' is the wordplay.
I cannot quite see how this works, but
'a' could be 'an' and 'an' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'like' acts as a link.
Can you help me to learn more?
(Other definitions for trojan that I've seen before include "Paris who abducted Helen was such a prince" , "Sort of horse" , "This war involved the kidnapping of fair Helen" , "Native of Troy" , "one typically hard-working" .)