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There exist at least 20 different designs for electronic circuits producing sine waves (with transistors, opamps, OTA´s). Without knowing some details (amplitude, exactness, tuning capabilities, max. THD,...) one cannot recommend a specific circuit. You should spend some time to collect, compare, review and evaluate some common realization principles.
If you have 5MHz square wave (quartz) clock with suitable output you could use LC band pass filter at that frequency followed by linear buffer.
If the distortions are not acceptable use another 5MHz LC band pass filter.
RC filters are not good enough in most of the cases for that purpose.
Also, you could see https://www.national.com/an/AN/AN-263.pdf