Castigate pace of progress (4)
I believe the answer is:
rate
I believe this is a triple definition!
'castigate' is the first definition.
(thesaurus)
'pace' is the second definition.
(synonyms)
'of' is a link.
'progress' is the third definition.
(thesaurus)
(Other definitions for rate that I've seen before include "Velocity" , "Measure of frequency; merit" , "Assess the value of" , "Pace" , "The price paid" .)