"Flag" can have many meanings, literal and figurative, as a noun or a verb. We will need context. Do you have the sentence with the advice?

flag noun noun: flag; plural noun: flags 1.a piece of cloth or similar material, typically oblong or square, attachable by one edge to a pole or rope and used as the symbol or emblem of a country or institution or as a decoration during public festivities. "the American flag" synonyms: banner, standard, ensign, pennant, banderole, streamer, jack, gonfalon 2. a device, symbol, or drawing typically resembling a flag, used as a marker. "golf courses are indicated by a numbered flag on the map" COMPUTING: a variable used to indicate a particular property of the data in a record. 3. a hook attached to the stem of a musical note, determining the rhythmic value of the note. verb verb: flag; 3rd person present: flags; past tense: flagged; past participle: flagged; gerund or present participle: flagging 1. mark (an item) for attention or treatment in a specified way. "“greatfully” would be flagged as a misspelling of “gratefully.”" synonyms: indicate, identify, point out, mark, label, tag, highlight "flag the misspelled words" draw attention to. "problems often flag the need for organizational change" AMERICAN FOOTBALL: charge (a player) with a penalty by dropping a penalty flag. "a play in which he was flagged for being offside" 2. direct (someone) to go in the specified direction by waving a flag or using hand signals. "have him flagged off the course" signal to a vehicle or driver to stop, especially by waving one's arm. "she flagged down a patrol car" (of an official in football, soccer, and other sports) raise or throw a flag to indicate a breach of the rules. "the rookie cornerback managed to get flagged for three penalties in one game" 3. provide or decorate with a flag or flags. register (a vessel) in a specific country, under whose flag it then sails. "the flagging out of much of the fleet to flags of convenience"