Jamieson, Fausset and Brown on Joel 1:9

9. The greatest sorrow to the mind of a religious Jew, and what ought to impress the whole nation with a sense of God's displeasure, is the cessation of the usual temple-worship.

meat offering--Hebrew, mincha; "meat" not in the English sense "flesh," but the unbloody offering made of flour, oil, and frankincense. As it and the drink offering or libation poured out accompanied every sacrificial flesh offering, the latter is included, though not specified, as being also "cut off," owing to there being no food left for man or beast.

priests ... mourn--not for their own loss of sacrificial perquisites (Nu 18:8-15), but because they can no longer offer the appointed offerings to Jehovah, to whom they minister.