This writer's wanting agreement to make impression (6)
I believe the answer is:
impact
'impression' is the definition.
(thesaurus)
'this writer's wanting agreement' is the wordplay.
'this writer's' becomes 'im' (the person writing the crossword clues).
'wanting' means one lot of letters go next to another.
'agreement' becomes 'pact' (pact is a kind of agreement).
'im'+'pact'='IMPACT'
'to make' is the link.
(Other definitions for impact that I've seen before include "Significance" , "Force of blow or collision" , "Repercussion" , "Bear upon" , "Crash" .)