Not sure exactly what you mean here.
Is the whole seat itself loose, ie, does the seat turn on the blank even when there's no reel attached? If so, try some epoxy poured between the seat and the blank. If that doesn't help, you're going to have to have the rod stripped, the seat re-attached and the guides re-wrapped.
Is the reel still loose even when the locking ring is tightened all the way down? If so, the hoods on the seat are too big for the reel foot. Try a different reel.
Is the reel loosening up after a few casts? If so, your hand is probably loosening the locking ring as you cast and fish. You can try taping the ring to prevent your hand from loosening it. And next time, have a custom rod built with the locking ring at the tip end of the reel seat
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