Panel of women popular within racecourse (8)
I believe the answer is:
wainscot
'panel' is the definition.
(wainscot is a kind of panel)
'women popular within racecourse' is the wordplay.
'women' becomes 'w'.
'popular' becomes 'in'.
'within' means one lot of letters goes inside another.
'racecourse' becomes 'ascot' (I've seen this before).
'in' inserted within 'ascot' is 'ainscot'.
'w'+'ainscot'='WAINSCOT'
'of' is the link.
(Other definitions for wainscot that I've seen before include "Lining of a wood-panelled wall" , "Wooden wall lining" , "panels" , "Wooden room lining/panelling" , "Lower part of interior wall" .)