A measure of advancement (4)
I believe the answer is:
step
I believe this is a double definition.
'a measure' is the first definition.
(step is a kind of measure)
'advancement' is the second definition.
(I've seen this in another clue)
'of' is the link.
(Other definitions for step that I've seen before include "short distance" , "Gradation" , "Prefix meaning related by remarriage" , "Footprint" , "Measure - pace" .)