S. R. Faruqi:

[For SRF's discussion of this ghazal as a whole, see {949,1}.]

In this verse, there's an uncommon combination of melancholy sorrow and a feeling of the going-to-waste of skill/ability. There are also some layers of meaning. For example, there can be several reasons for Mir's enchantment of expression to be mingled with the dust: (1) Mir himself is living, but because of the disasters of the age, grief over the beloved, the decline of his poetic powers, etc. his 'enchantment of expression' ( = poetry) is finished. (2) Even now Mir composes poetry, but but for some reason (or for one of the aforementioned reasons) now 'enchantment of expression' no longer remains in his poetry. (3) 'Enchantment of expression' was a quality of his style of reciting verses, as in the second divan [{718,2}]:

jādū kī paṛī parchah-e abyāt thā us kā
muñh takye ġhazal paṛhte ʿajab siḥr-bayāñ thā

[a magic spell was the page of his verses
if one would stare at his face/mouth while he was reciting ghazals, there was an extraordinary 'enchantment of expression']

That is, the 'enchantment of expression' was connected both with the nature of his poetry, and with his manner of presentation. When Mir went away, then the presentation went away. But his verses remain.

We should also reflect on this point: that the mention is of his 'style' of speech, not the 'truthfulness' of his speech, or its 'sincerity', or its 'social consciousness', etc., because Mir (and all our classical poets) knew very well that the spirit of poetry is in this style of expression, not in its so-called 'philosophical', 'intellectual', 'didactic', etc., aspects.

Maulana Hasrat Mohani divided the themes of the ghazal into philosophical, mystical, and so on, and thus did the great harm of causing people to think that the standards of goodness and badness of the ghazal's verses were the same as those of its kinds of themes. Thus although he acknowledged 'immoral' [fāsiqānah] themes, this word is in moral terms so negatively 'loaded' and so full of unpleasant meanings that it could never attain the rank of a critical term.

In classical ghazal there were certainly standards for the excellence of a theme, but they were not based on a division into immoral, lover-like, etc. This division is entirely artificial, and is contrary to classical speech and practice. Then there's also the fact that (as we have seen here and there in this work) one single verse can be the bearer of philosophical, lover-like, mystical themes all at once.

FWP:

SETS == POETRY
MOTIFS
NAMES
TERMS == IZAFAT

For discussion of this ghazal as a whole, see {949,1}.

For the 'enchantment of expression' to have been finally mingled with the dust evokes the dastan world, in which the breaking of a 'tilism', a special enchanted world, usually results in, or at least coincides with, the death of the magician who created it. The theme of magic continues in the next verse, {949,6}.

Note for grammar fans: To join siḥr-bayānī in this way seems to makd it a case of an 'omitted' izafat.