Get garage to change total (9)
I believe the answer is:
aggregate
'total' is the definition.
(synonyms)
'get garage to change' is the wordplay.
'to change' is an anagram indicator.
'get'+'garage'='getgarage'
'getgarage' anagrammed gives 'AGGREGATE'.
(Other definitions for aggregate that I've seen before include "Accumulate into total" , "Collective total - a great egg (anag)" , "small stones" , "All - broken stone put in cement" , "Collected" .)