Insist upon (6)
'insist upon' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for demand that I've seen before include "Imperious request as for payment" , "Urgent or peremptory request" , "Insistent request" , "Require, need" , "Ask peremptorily or call for" .)
'insist upon' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for urge that I've seen before include "Yen" , "Encourage to proceed, drive onward" , "Try hard to persuade, advise earnestly" , "Press to do something" , "Press; drive" .)