Can I write off clothing I had to buy to work for my employer?

W-2 employees cannot deduct job-related expenses on a federal return.  Job-related expenses were eliminated as a federal deduction for W-2 employees by the tax laws that changed for 2018 and beyond.  Your state tax laws might be different in AL, AR, CA, HI, MN, NY or PA.

If you live in a state that lets you deduct job-related expenses, the information will flow from your federal return  to the state return, so enter it in Federal>Deductions and Credits>Employment Expenses>Job-Related Expenses

Simple answer--the IRS says no--UNLESS it is clothing that is a uniform, clearly branding you as a worker. So if you can get it off the shelf and wear it most anywhere, that's a no :-(. 

On the other hand, if it's a statue of liberty costume to wear waving people down on the street, that would be a yes.
It it's a judgement call, make your best judgment and the IRS will probably never ask you about it anyway.

So if it's tan slacks and a red polo with a discrete brand name and you are always saying, "It's my pleasure," you can probably deduct the cost even if you occasionally wear it to church when your workplace is closed ;-). (Do they make their workers pay for those?)