Aggressive talk making British leader shine in the USA (7)
I believe the answer is:
bluster
'aggressive talk' is the definition.
'bluster' can be an answer for 'talk' (thesaurus). I'm not sure about the 'aggressive' bit.
'british leader shine in the usa' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in BBC).
'leader' says to take the initial letters.
'in the' is an insertion indicator.
'usa' becomes 'luter' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'shine' is 's'.
's' put within 'luter' is 'luster'.
'b'+'luster'='BLUSTER'
'making' is the link.
Can you help me to learn more?
(Other definitions for bluster that I've seen before include "Swagger" , "Talk aggressively to little or no effect" , "Boastful and bullying talk" , "Brag (to hide fear)" , "Empty boasting" .)