Are you military? If so, while that clothing allowance was added to your paycheck, you were not taxed on it. Therefore you can't deduct it.

No, I work for my City and have to buy uniforms. They give me $600.00 a year for clothing allowance. This is put in my pay check with my hourly rate pay. It is not put in separate.

Thanks for the additional info. If this $600 is listed on your W-2 in box 12 with code L, then while it is included in box 1, it has already been excluded from taxable income and can't be claimed/reported anywhere else on your tax return.
Otherwise, you will report your employment expenses under the Deductions & Credits tab in the Job Related Expenses section when you get to it. Note that these would be expenses required for employment, or continued employment.