Chocolatiers have large plant by western side of racecourse (8)

'racecourse' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'chocolatiers have large plant by western side' is the wordplay.
I cannot really see how this works, but
'have' could be 'own' ('own' can be a synonym of 'have') and 'own' is found in the answer.
'plant' could be 'tree' (tree is a kind of plant) and 'tree' is found within the answer.
'side' could be 'r' (abbreviation for right) and 'r' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

'of' is the link.

Can you help me to learn more?