Record thus maintained primarily in racecourse (5)
I believe the answer is:
epsom
'racecourse' is the definition.
(I've seen this before)
'record thus maintained primarily' is the wordplay.
'record' becomes 'ep'.
'thus' becomes 'so' (synonyms).
'primarily' indicates taking the first letters.
The first letter of 'maintained' is 'm'.
'ep'+'so'+'m'='EPSOM'
'in' is the link.
(Other definitions for epsom that I've seen before include "Derby area" , "Mopes around in English horse-racing venue" , "Downs" , "Location of English Derby" , "Mares would triumph here" .)