Supporter opposing trouble shows boldness (7)
I believe the answer is:
bravado
'boldness' is the definition.
(I've seen this before)
'supporter opposing trouble' is the wordplay.
'supporter' becomes 'bra' (a bra gives support to breasts).
'opposing' becomes 'v' (abbreviation for versus).
'trouble' becomes 'ado' (both can mean bother or commotion).
'bra'+'v'+'ado'='BRAVADO'
'shows' acts as a link.
(Other definitions for bravado that I've seen before include "A show of boldness, may be phoney" , "Swag" , "Boastful courage" , "Swaggering show of false courage" , "Swaggering show of boldness" .)