On board, he usually looks a bit horsy (6)
I believe the answer is:
knight
This clue might be a double definition.
'on board' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'he usually looks a bit horsy' is the second definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
Can you help me to learn more?
(Other definitions for knight that I've seen before include "board member" , "Give title to; chess piece" , "Titled man - chessman" , "... for example, Tippett" , "Chivalrous warrior of olden times" .)