FWP:
SETS ==EK; EXCLAMATION
This one was a bit confusing; I was glad of Nazm's strong lead (and so were the other commentators, I suspect). Ghalib's own paraphrase also suggests that Nazm is on the right track. Since both la;z;zat and sa((ii are feminine, there can be some confusion as to what's at risk of going down into the dust; and the grammar of the second line opens several conceivable ways to parse it (what does hamaarii modify? what does the jo really apply to?). On the whole, though, I think teasing out those small permutations doesn't add any real pleasure to the verse, or provide any fresh or valuable readings, so I'll refrain.
There are plenty of small word- and meaning-plays: pleasure versus despair; one versus a crowd (see the definition of hujuum above); a rush or attack, versus a passive going down into the dust. The secondary meaning of hujuum as 'effort' resonates particularly well: we have then an 'effort of despair' in the first line and a 'fruitless effort' in the second line.
The speaker is exclaiming to a rush or attack of despair, urging it to back off, for fear that something feminine singular will be trampled into the dust in the crush. In classic mushairah style, the first line is cryptic and incomplete, but tantalizing, so that we wait impatiently to hear what all the fuss is about. Even the first half of the second line gives us no real clue, except that it's probably something valuable and unique (though the remarkable multivalence of ek leaves a lot of room for maneuver). Not until the rhyming elements do we learn that the precious, vulnerable thing in need of protection from the rush or despair is the speaker's 'fruitless endeavor'.
But having enjoyed the realization and the wordplay, is there anything more? Beyond the level of wordplay, the verse doesn't really seem to hang together very well. If the 'endeavor' is something that can be trampled into the ground by a rush or attack of despair, it seems that it might be at least somewhat personified. But then the effort, though fruitless, is a special (unique? sole?) source of pleasure; and it's in danger of being destroyed by the rush/attack/'effort' of despair. So is the 'effort' of despair successful (in overpowering the speaker's 'fruitless endeavor'), while his own 'effort' remains perpetually unsuccessful? Or is his 'fruitless endeavor' what generates the 'rush/effort of despair' in the first place? The verse refuses to click into place in any exciting way. The four primary images-- rush/attack; going into the dust; pleasure; and fruitless endeavor-- are simply not richly intermeshed with each other, as they so often are in Ghalib's great verses. This one lacks the deeper kinds of connection.
But then, there's always a 'connection' with the figure of Sisyphus:
Ghalib:
[1865, to Majruh:] How can I describe the state I'm in? Formerly I used constantly to recite this verse of mine: {157,4}. Now I'm no longer even fit for that kind of tune. That is, the pleasure of my fruitless endeavor has gone down into the dust [sa((ii-e be-;haa.sil kii la;z;zat ;xaak me;N mil ga))ii]. (Arshi p. 305)
==Urdu text: Khaliq Anjum vol. 2, p. 543