Horse-rider requests trial, one totally unlimited (10)
I believe the answer is:
equestrian
'horse-rider' is the definition.
(I've seen this before)
'requests trial one totally unlimited' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'an' ('a' and 'an' can mean 'one') and 'an' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for equestrian that I've seen before include "Horse-rider" , "Person on horseback" , "Jockey" , "Horseman" , "Relating to horse riding" .)