一只 or 一支 meaning only or a unit
When 只 is used after 一，it is always interpreted as a measure word.
If you want to say &quot;A video for you only&quot;, it will be &quot;一段只给你的视频&quot;, or &quot;只给你的视频&quot;.
Also the character 只 as a measure word evolves from the action of catching a bird:
 Source:http://qiyuan.chaziwang.com/etymology-14538.html
Therefore it is mostly used on animals:
一只鸟 a bird
一只狗 a dog
一只老鼠 a mouse
or body part:
一只手 a hand
一只脚 a foot