Definition: In this task, you need to remove all words of a given length in the sentence. The number of letters in a word determine its length, for example, the length of the word "apple" is 5.
Input: Sentence: 'a man in military gear with a gun crouching behind a rock structure with a banana tree in front of him'. Remove all words of length '1' in the given sentence.

man in military gear with gun crouching behind rock structure with banana tree in front of him