Racecourse record some cannot complete (5)
I believe the answer is:
epsom
'racecourse' is the definition.
(Epsom is an English racecourse)
'record some cannot complete' is the wordplay.
'record' becomes 'EP' (abbreviation for extended play record).
'cannot complete' means to remove the last letter.
'some' with its last letter taken away is 'som'.
'ep'+'som'='EPSOM'
(Other definitions for epsom that I've seen before include "Mares would triumph here" , "place for racing" , "Home to the Derby and the Oakes" , "Poems about English Derby venue" , "Derby area" .)