HI,
Standard SAP can able deduct withholding tax while doing invoice posting.
I think you are defining tax code with accumation for a vendor , which is having exemption. If there is exemption , the vendor should not be one time vendor.
Also FTXP is forn input out tax codes(Indirect Taxes) , TDS is different tax. If you need to check the TDS check in SPRO -Define Withholding Tax Codes
Hope it would help you.
Regards
pankaj Pandey