Dimension of intensity (5)
I believe the answer is:
depth
This clue is a double definition.
'dimension' is the first definition.
(thesaurus)
'intensity' is the second definition.
(thesaurus)
'of' acts as a link.
(Other definitions for depth that I've seen before include "Distance downwards" , "Measure" , "Distance from top down as in water" , "Insight" , "Measurement from front to back" .)