We have a thread for enquiries like yours. If you re-post your question with as much detail as possible in the Help With Family Histories and Mysteries
thread you will have a better chance of a response. Please note though that we are a royal-related site rather than a genealogical research site. Good luck!
I've just had a look and in this page of The Belgian Nobility
the name of de clercq
appears in the column headed 'Nobility only, with the optional title of "Esquire" [Untitled Nobility].
A Google search under the name of de clercq brings up a very large number of entries.