Type of horse that starts each of Goodwood races every year (4)

I believe the answer is:

grey

I'm a little stuck... Click here to teach me more about this clue!

'type of horse' is the definition.
'grey' can be an answer for 'horse' (I've seen this before). I am unsure of the 'type of' bit.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for grey that I've seen before include "Dismal - colour" , "Neutral tone between black and white" , "Colour, between black and white" , "Intelligence" , "Black-white tone" .)

I've seen this clue in The Independent.

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