Giant deficit breaks firm associated with America (8)
I believe the answer is:
colossus
'giant' is the definition.
(I know that giant can be written as colossus)
'deficit breaks firm associated with america' is the wordplay.
'deficit' becomes 'loss' (I've seen this before).
'breaks' is an insertion indicator (inserted letters break into the word).
'firm' becomes 'co' (a firm is a company).
'associated with' means one lot of letters go next to another.
'america' becomes 'US' (United States).
'co'+'us'='cous'
'loss' inserted within 'cous' is 'COLOSSUS'.
(Other definitions for colossus that I've seen before include "huge figure" , "An immense state as once at Rhodes (8)" , "Something larger than life" , "The - - of 19" , "Giant statue once at Rhodes" .)