It is always good to mention what engine your vehicle has, particularly with engine and exhaust issues. It would be better still to put this in your sig or profile so it shows up on the left panel with every post.
If I am interpreting your picture correctly, you mean that the pipe on the front of the flexible section has come off the flexible section? If so that was one piece welded together as far as I can tell, no clamp attaching it.
If so there are two usual economy options, either have an exhaust shop weld it back on (usually very inexpensive), or if it is too rusted for there to be enough material to weld to, the flexible section is replaced by welding in a new one, pricing varies in regions and shops but usually $120-ish for other vehicles in the past.
I could be wrong, I mean I see a clamp behind the pipe connected to the flexible section but not so close in front of it. There's also the OEM shop way, the higher priced option to buy the OEM pipe, or a shorter lived aftermarket, including the flexible section and it connects further up in the picture than shown, then based on the corrosion, you may need the rear clamp too, the front gasket, and front bolts if degraded badly. For example here "could" be that entire part if you have the 2.0L EB engine:
Their diagram also shows a (welded on?) hanger stud and #8133 rubber hanger so that should be looked at and reconnected if off or replaced if torn, again if you have the 2.0L engine/exhaust, maybe the others are the same but it really is best to know what engine ahead of time!
I'd call a few exhaust shops, explain that you have a pipe that broke off the flexible section and get a quote for welding it back on, even if just a ballpark estimate over the phone. Maybe it needs more, because it does look like it rusted to a weakened state, but at least this gives you an idea where their labor prices start for what is a relatively simple repair if up on a rack instead of crawling under to DIY.
If you want to get the OEM part I wouldn't blame you, probably worth the extra money to offset labor costs unless replacing it yourself, might find best price on White Bear Lake Ford's site but it wouldn't hurt to call a local dealer shop too, in case postage swamps the price difference, or use the part # on their site to search prices elsewhere.
"IF" you have the 2.0L engine, this looks like the OEM pipe for it:
2012-2015 Ford Explorer part # DB5Z-5G274-A - Exhaust Pipe
parts.autonationfordwhitebearlake.com
Having written all that, from your pic, it looks more like you have the 3.5L engine and if so the same principles as above apply but the whole OEM assembly is a larger pipe that costs more, may be the following part #1, and this is also available as a cheaper, probably shorter lived aftermarket part on Rock Auto. I'd still check on welding it first, or muffler shops stock *generic* flex pipe sections, cheaper than custom made assemblies, just depends on how much rust has set in on the existing pipe, whether it's viable to weld to.
parts.autonationfordwhitebearlake.com
You could try throwing a regular U-bolt style pipe clamp on to hold it temporarily but I doubt it's going to last long as there just isn't enough length there, nor at the pipe flare area, to get a good grip, plus if there's too much rust it may just further disintegrate the pipe flare area when you tighten it down.
