when engine is warmed up,,I have a ticking noise which I think is from around the drive belt on a 2008 fusion 1.6 petrol,,,any ideas

Years ago I had a 2001 focus 1.6 petrol. It kept making an erratic clicking more of a click than tick and not a steady beat.  Mainly when cold.  I could not find what it was so put up with it.  Then one day I was 100 miles from home and the alternator belt came off. Turned out the spring loaded tensioner wheel , plastic, had melted. The bearing had seized so the belt being dragged round the stuck plastic wheel caused lots of heat and it melted so belt came off.  The bearing failing was the clicking that I had heard for weeks, probably months.  Luckily I had rac so they brought car home where I fixed it myself.  The belt drove the water pump so I could not drive home.  Had it been an engine with water pump driven by timing belt like some cars have I could have carried on until battery was flat.  Don’t know if I would have got all the way.  Was daylight so maybe.  Yours might be a different problem but just letting you know what happened to me. 

Thank you,,could be something similar,,it seemed to come on after the very hot day we had,,will have to get it checked at garage.