Keep demonstrating reticence (7)
I believe the answer is:
reserve
I believe this is a double definition.
'keep' is the first definition.
(I know that reserve is a more specific form of the action keep back)
'reticence' is the second definition.
(I know that reticence can be written as reserve)
'demonstrating' is the link.
(Other definitions for reserve that I've seen before include "Modesty- store" , "Reticence" , "not in the front line" , "Conservation area" , "Wine kept" .)