Said to be full of agreement (4)
I believe the answer is:
pact
'agreement' is the definition.
(pact is a kind of agreement)
'said to be full' is the wordplay.
'said to be' shows a homophone (sound like).
'full' becomes 'packed' (synonyms).
'packed' sounds like 'PACT'.
'of' is the link.
(Other definitions for pact that I've seen before include "Treaty, formal agreement" , "deal" , "Agreement, bargain" , "International treaty" , "'Accord, treaty (4)'" .)