Capacity to be satisfied (7)
I believe the answer is:
content
I believe this is a double definition.
'capacity' is the first definition.
(I know that capacity can be written as content)
'be satisfied' is the second definition.
(similar in meaning)
'to' acts as a link.
(Other definitions for content that I've seen before include "what's included" , "Gist" , "substance of book?" , "Quietly happy" , "Satisfied; volume" .)