If your data is coming back as a string of words seperated by a comma then you could try the following.
See full flow below. I'll go into the actions.

Data is a Compose action that contains the data. This would be the property you already have.

Filter array splits the data by comma, then checks to see if a lowercase version of each item contains 'office'. This will cater for uppercase, lowercase, mixed case, etc. The expressions used are below:
//From - you would replace outputs('Data') with your property
split(outputs('Data'), ',')
//Filter
toLower(item())

Compose retrieves the first item from the Filter array and trims any leading/trailing spaces giving you what you're after. The expression used is:
trim(first(body('Filter_array')))

This should give you the result regardless of where it is in the string.
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