Synonyms of 'hobby-horse'
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If you accuse a person of having a fixation on something or someone, you mean they think about a particular subject or person to an extreme and excessive degree.
Somebody has a fixation with you.
If you say that someone has an obsession with a person or thing, you think they are spending too much time thinking about them.
yet another man with an obsession about football
Thesaurus for hobby-horse from the Collins English Thesaurus
You describe a subject or idea as your hobby-horse if you have strong feelings on it and like talking about it whenever you have the opportunity .