UK standard visitor visa sponsored by my mother

The UK Immigration Rules https://www.gov.uk/guidance/immigration-rules/immigration-rules-appendix-v-visitor-rules on funds, maintenance and accommodation provided by a third party state that: V 4.3 A visitor’s travel, maintenance and accommodation may be provided by a third party where the decision maker is satisfied that they: (a) have a genuine professional or personal relationship with the visitor; and (b) are not, or will not be, in breach of UK immigration laws at the time of decision or the visitor’s entry to the UK; and (c) can and will provide support to the visitor for the intended duration of their stay.

Therefore you can use your mother’s Fixed Deposit account provided it meets (c) above e.g. there are no restrictions on withdrawals from the account that would mean the funds would not be available to you during your visit. You will also need to provide evidence showing the source of the funds in the Fixed Deposit account.

As the applicant, you still have to show that you meet the requirements in your own right. Needing a sponsor may increase the likelihood of rejection.