On which to make a start in motor sport (4)
I believe the answer is:
grid
'motor sport' is the 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?
'on which to make a start' is the wordplay.
'on which' becomes 'gri' (I can't justify this - if you can you should believe this answer much more).
'to make' becomes 'do' (do can mean to make or prepare).
'a start' means to remove the last letter (I've seen 'starts' mean this).
'do' with its final letter taken off is 'd'.
'gri'+'d'='GRID'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for grid that I've seen before include "Rectangular framework" , "Network of horizontal and vertical lines" , "Rectangular lattice" , "Bars used to make one" , "Regular pattern of horizontal and vertical lines" .)