Thing jumping ahead of horse trial (9)
I believe the answer is:
nightmare
'trial' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'thing jumping ahead of horse' is the wordplay.
'jumping' indicates an anagram.
'ahead of' says to put letters next to each other (some letters go in front of others).
'horse' becomes 'mare' (mare is a kind of horse).
'thing' with letters rearranged gives 'night'.
'night'+'mare'='NIGHTMARE'
Can you help me to learn more?
(Other definitions for nightmare that I've seen before include "Awful experience" , "Frightening dream" , "It makes one restless" , "Terrifying dream" , "dreadful experience" .)