This is how I analyzed it. May be the lyrics aren't that intense and Gulzar literally meant what he wrote.
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meraa kuchh saamaan tumhaare paas padaa hai
She is reminiscing the times they spent together
saawan ke kuchh bheege bheege din rakhhe hain
This is the turbulent phase of their relationship
aur mere ik khat mein liptii raat padii hai
And memoir contains the details of that night or phase
vo raat bujhaa do
She wants to erase the memory associated with that phase
meraa vo saamaan lautaa do ..
Starting afresh but not together