No. If you already have a valid UK visa, you generally do not need to apply for a separate UK ETA.
A UK ETA is for eligible travelers who can visit the UK without a visa and need travel authorization in advance.
Therefore, if you already have valid permission to enter the UK, such as a UK visa, residence permission, work permission, or study permission, you do not need a UK ETA.
However, if your visa has expired or does not match your current travel purpose, you may need to check whether a new visa or UK ETA is required.