Racecourse to keep so many content (5)
I believe the answer is:
epsom
'racecourse' is the definition.
(Epsom is an English racecourse)
'keep so many content' is the wordplay.
'content' indicates a hidden word (letters contained within the clue).
'EPSOM' is hidden within 'keep so many'.
'to' acts as a link.
(Other definitions for epsom that I've seen before include "Racecourse near London" , "Classic venue" , "English racecourse" , "Classic racecourse" , "Derby town" .)