Initially I used to teach to call clear prop since that was what I was taught but over the years I've moved more & more towards not bothering, instead emphasizing to have a bloody good look around unless it relates to a maintenance related action eg working with an engineer who needs the donk started.
Rationale:
1: It's almost never done in commercial ops anyway
2: As mentioned by others above, no one except the aviation literate have a clue about meaning, and they tend to give a wide birth to an a/c that has crew seats occupied
3: Few, if any, making the call ever wait long enough for a 'victim' recipient to move away.
4: How many would hear the call in a busy airport over the noise of lots of other a/c starting, taking off or even just taxiing past?
5: And finally, if a warning call to aviation ignorant is necessary under the circumstance then I prefer something like 'Stand clear'. A general principle of communication is to avoid using specialist jargon if you wish your vocalisation to have any meaning to those not privy to that field of knowledge.
Far better, I think, to have a bloody good look around and stick any fitted beacons/lights on.