Ate without complaint, being satisfied (6)
I believe the answer is:
filled
'satisfied' is the definition.
('fill' can be a synonym of 'satisfy')
'ate without complaint' is the wordplay.
'ate' becomes 'fed' ('feed' can be a synonym of 'eat').
'without' is an insertion indicator ('without' can be similar in meaning to 'outside').
'complaint' becomes 'ill' ('ill' can be a synonym of 'complaint'**).
'fed' enclosing 'ill' is 'FILLED'.
'being' is the link.
(Other definitions for filled that I've seen before include "Topped up" , "Occupied the whole of" , "Glutted" , "Repleted, satiated" .)