Nigel and Ray trained a young racehorse (8)
I believe the answer is:
yearling
'a young racehorse' is the definition.
(I've seen this before)
'nigel and ray trained' is the wordplay.
'and' is a charade indicator (letters next to each other).
'trained' indicates anagramming the letters (to train can mean to grow something into a shape).
'nigel' after 'ray' is 'raynigel'.
'raynigel' is an anagram of 'YEARLING'.
(Other definitions for yearling that I've seen before include "Animal aged one" , "Animal in its second 12 months" , "Young racehorse" , "Youngster" , "Twelve-month old animal" .)