i was marked wrong for "a shoe" but as of now duo does not accept it as correct (13 aug 2018)
For the given translation to be correct there should be stress on the word एक , which isn't there, my answer -- that man wears a shoe, wasn't accepted!
The translation above is a very emphatic and rare sentence in English. I think it must be wrong. I think it is (a pair of) shoes???? That would make sense. I think I have heard it used in this way.
poor man - he must have lost a leg! That said, जूता can also mean 'a pair of shoes', according to 'Complete Hindi', page 440 by Rupert Snell
Unlike English, in which is wearing and wears mean exactly the same thing, in Hindi, there's a different tense for is wearing, I think it's called the present continuous. For that tense you say That man one shoe pehen reha he (sort of wear-ing-is). You shorten the main verb and add reha (sorry, I can't type in Hindi).
I think the problem is mostly that पहनना does not mean 'to wear', but actually means 'to put on'. For example, to say 'What a nice kurti you're wearing!' you could say 'कितनी अच्छी कुर्ती तुमने पहनी!', which literally translates to 'What a nice kurti you put [preterit] on!'. Thus 'is wearing' is different from 'is putting on', while the latter is similar to 'पहन रहा है'. Hope that helps!