Get garage to adjust total amount (9)
I believe the answer is:
aggregate
'total amount' is the definition.
(I've seen this in another clue)
'get garage to adjust' is the wordplay.
'to adjust' is an anagram indicator.
'get'+'garage'='getgarage'
'getgarage' with letters rearranged gives 'AGGREGATE'.
(Other definitions for aggregate that I've seen before include "Total of several separate elements" , "Combine into a whole" , "A whole formed by combining several elements" , "The whole amount" , "Combined or total amount" .)