Hello,
Please note that questions like this are outside the scope of the support channel.
Are you entering timesheets via the following view?
If so, the following CSS should do the trick:
html#p-ts-workitem-timesheets select[id^="editorContainer"][id$="selectDuration"] option[value="min"] {display: none;}
html#p-ts-workitem-timesheets select[id^="editorContainer"][id$="selectDuration"] option[value="d"] {display: none;}
I hope this helps.
Roland