Eg, equestrian (5)
I believe the answer is:
rider
'eg equestrian' is the definition.
(equestrian is a kind of rider)
This is all the clue.
(Other definitions for rider that I've seen before include "Supplementary verdict brought in by jury" , "Catch" , "One in the saddle" , "Appandix, codicil" , "Jury's added comment" .)