indicator

noun

1. A pointer or index that indicates something.

   “The visual indicators are a decided improvement, and have reduced the telephoning by the staff in the signalbox.”

   “These old indicators [at Earl's Court station] show the destination of the next train by the appearance of an illuminated arrow next to the station name. The arrow may indicate that a train is going to Wimbledon, but it gives no clue as to when. Now, however, the indicators are supplemented by dot matrix panels that not only say where but also when. Why aren't the old ones removed? Because they, like the whole station, are Grade II listed.”

   “The phrase was, and remains, a double-edged sword: a testament to the hard-working and hard-living citizens of the Crescent City and an indicator of the “ah, whatever” shrug hanging over its corrupt politics, its ramshackle infrastructure and its belief that partying trumps all.”

2. A meter or gauge.
3. The needle or dial on such a meter.
4. Any of many substances, such as litmus, used to indicate the concentration of a substance, or the degree of a reaction.
5. A plant or animal whose presence is indicative of some specific environment.
6. A measure, such as unemployment rate, which can be used to predict economic trends.
7. (Australia, Ireland, New-Zealand, South-Africa, UK)A turn signal; each of the flashing lights on each side of a vehicle which indicate a turn is being made to left or right, or a lane change etc.
8. A bird, the honeyguide.
9. A codeword that marks the use of a specific cryptic device.

   “'Wild' is an anagram indicator showing that the letters of 'danger' have to be rearranged.”

   “We surrounded the strike, Snowy (5) Snowy is the definition in this clue. Ignore the punctuation and capital letter of Snowy! Surrounded is the container indicator.”

   “We have already mentioned 'in' having multiple uses; 'round' or 'around' might be a container indicator or a reversal indicator; 'without' might be a container indicator or a deletion indicator, and so on.”