There is currently no plugin offering names that can be directly clicked. But you can try the SourceCookifier plugin along with some N ++ settings. Open N ++ "contextMenu.xml" and add this line somewhere:
<Item PluginEntryName="SourceCookifier" PluginCommandItemName="Go To Definition"/>
At least the solution is to have it with two clicks> right click> context menu> "Go to definition". I would say just press CTRL + SHIFT + RETURN when the cursor is on a character that also performs "Go to definition", but since you asked for a mouse button approach.
/ EDIT
A plugin update has appeared these days. Here is a snippet from the change log:
0.7.1
-new: option "Go to definition by pressing Ctrl + left mouse button "
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