Price of horse shortened (6)
I believe the answer is:
charge
'price' is the definition.
(I've seen this before)
'horse shortened' is the wordplay.
'horse' becomes 'charger' (charger is a kind of horse).
'shortened' means to remove the last letter.
'charger' with its final letter removed is 'CHARGE'.
'of' is the link.
(Other definitions for charge that I've seen before include "Accuse; load, fill" , "Lord Cardigan's order to his brigade" , "protection" , "Rush to exact payment?" , "Price for a service" .)