In plain words
Where all has burnt down to ash in the stream of the sahasrāra, pour again the great rain of Your compassion, and feed the devotion to You that has already sprouted, abode of grace. Salutation to Nārāyaṇa.
Word for word
In this ash, in the stream of the sahasrāra that has burnt well, pouring the great rain of Your compassion again, add manure now to the devotion to You that sprouted before, O abode of grace. Salutation to Nārāyaṇa.