Agree the amount (5)
I believe the answer is:
tally
This clue is a double definition.
'agree' is the first definition.
(synonyms)
'the amount' is the second definition.
(thesaurus)
(Other definitions for tally that I've seen before include "Match - score" , "Running total" , "List" , "Agree, add up" , "Count up; match" .)