Administration of incomplete diet (6)
I believe the answer is:
regime
'administration' is the definition.
(thesaurus)
'incomplete diet' is the wordplay.
'incomplete' means to remove the last letter.
'diet' becomes 'regimen' (I've seen this before).
'regimen' with its final letter removed is 'REGIME'.
'of' is the link.
(Other definitions for regime that I've seen before include "The government in power or systematic plan" , "Government; ordered way of doing something" , "Routine" , "Government, especially an authoritarian one" , "co-ordinated programme" .)