Brigadier General Clingan enlisted in the Marine Corps Reserve in 1989 and deployed to Operations DESERT SHIELD/STORM in 1990-91 with the 4th Civil Affairs Group.  He was commissioned in 1993 through the Naval Reserve Officer Training Corps program after graduating from the American University with a degree in International Studies. 
As a company grade officer, his operational assignments were Rifle Platoon Commander and Company Executive Officer, 2d Battalion, 1st Marines 1994-97; and Weapons and Rifle Company Commander, 3d Battalion, 3d Marines 2001-03 (Operation ENDURING FREEDOM – PHILIPPINES 2003).

As a field grade officer, his operational assignments were Operations and Executive Officer, Headquarters Battalion, 2d Marine Division 2006-07; Operations and Executive Officer, 3d Battalion, 6th Marines 2007-08 (Operation IRAQI FREEDOM 2007 & 2008); Current Operations Officer, G-3, 1st Marine Division (Forward) 2010-11 (Operation ENDURING FREEDOM 2010-11); Battalion Commander, 3d Light Armored Reconnaissance Battalion 2011-12 (Operation ENDURING FREEDOM 2012); G-35, Future Operations Officer, Marine Forces Europe and Africa 2014-16; and Assistant Division Commander, 3d Marine Division 2018-20; and Chief of Staff, III Marine Expeditionary Force 2020-21.  
 
His supporting establishment assignments include service as an instructor at The Basic School (TBS) 1997-2000, again as the Director of the Warfighting Instructor Group 2009-10, and a third time as the Commanding Officer 2016-18.
 
His joint duty assignment was as the Operations Officer, United Nations Command Military Armistice Commission, Republic of Korea, 2003-05. 
 
Brigadier General Clingan currently serves as the Assistant Deputy Commandant to Combat Development and Integration and Deputy Commanding General of Marine Corps Combat Development Command.

His professional military education includes: TBS Basic Officer Course (General’s Honor Roll) and Infantry Officers Course; Amphibious Warfare School (Distinguished Graduate); Weapons and Tactics Instructor (WTI) course; Marine Corps Command and Staff College (Distinguished Graduate with Masters of Military Studies); Naval War College, (President’s Honor Graduate/Highest Distinction with Masters of Strategic Studies).