Day Arab is given a hobby horse (9)
I believe the answer is:
monomania
'hobby horse' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'day arab is given a' is the wordplay.
'day' becomes 'mon' (short for Monday).
'arab' becomes 'Omani' (someone from Oman).
'is given' says to put letters next to each other.
'mon'+'omani'+'a'='MONOMANIA'
Can you help me to learn more?
(Other definitions for monomania that I've seen before include "obsessive single-mindedness" , "Unhealthy preoccupation with one thing" , "Single-minded passion" , "Obsession with one thing" .)