Lack of satisfaction (10)
I believe the answer is:
discontent
'lack of satisfaction' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for discontent that I've seen before include "Unhappiness" , "Lack of satisfaction" , "Now is the winter of our - (Richard III)" , "'Now is the 16 of our _____ made 2 15 by this sun of 7'" , "Dissatisfaction" .)