Urgency of hard master having no limits (5)
I believe the answer is:
haste
'urgency' is the definition.
(thesaurus)
'hard master having no limits' is the wordplay.
'hard' becomes 'h'.
'having no limits' indicates the central letters (the edge letters or limits are removed).
The centre of 'master' is 'aste'.
'h'+'aste'='HASTE'
'of' is the link.
(Other definitions for haste that I've seen before include "The more of it, the less speed, it is said" , "go at speed" , "Expeditiousness" , "Speediness or rush" , "furious activity" .)