How to remove the value for text field/text_area field

How to remove the value for text field/text_area field

I have 2 text field (1 text field and another 1 text area field)
If user enters the input into the (#accession_number) text field, then
suddenly realized it's the wrong field, they would have to click the
#FASTA_p to show (#FASTA) text area field and hide (#accession_number)
field.
Problem : The values of (#accession number) is still there even after
clicking hide . How should i totally remove the input user entered ?
For example: I chosed the wrong field and input my values but I haven't
click submit. I realized i entered in the wrong field, so i clicked
another field to enter my input but at the same time i want to remove the
values in the first field. How should i do that besdie asking user to do
it manually?