Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
punter [ˈpʌntər] n (BRIT) (gambler) (профессиона́льный) игро́к#; (inf)(customer) клие́нт(ка#)
the punters (inf) клиенту́ра fsg
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.