Explanation

Pakistan and India are cooperating to clean up the area of "Illegal " along their borders. 

ستان اور بھارت اپنی سرحدوں پر "غیر قانونی" کے علاقے کو صاف کرنے کے لیے تعاون کر رہے ہیں

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Another word used for "illicit " is Illegal 

Illegal is best to keep the meaning of the original sentence.

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The meaning of illicit drugs is one that is illegal and the non-medical use of drugs that are legally available.

illicit drugs are phrasal verb which means غیر قانونی منشیات

illegal meaning غیر قانونی