One of the more current and widely agreed on definitions is from political scientists Ken Kernaghan and John Langford in their book “The Responsible Public Servant”. They define self-dealing as “a situation where one takes an action in an official capacity which involves dealing with oneself in a private capacity and which confers a benefit on oneself."
Michael McDonald, Ph.D, Chair of Applied Ethics at The University of British Columbia provides examples based from this book: “You work for government and use your official position to secure a contract for a private consulting company you own.” and “using your government position to get a summer job for your daughter”.