Difficulty faced by loud American worrier (7)
I believe the answer is:
fusspot
'worrier' is the definition.
(synonyms)
'difficulty faced by loud american' is the wordplay.
'difficulty' becomes 'spot' (as in a spot of difficulty).
'faced by' means one lot of letters go next to another.
'loud' becomes 'f' (short for forte - 'loud' in music).
'american' becomes 'us' (abbreviation for United States).
'f'+'us'='fus'
'spot' after 'fus' is 'FUSSPOT'.
(Other definitions for fusspot that I've seen before include "One who gets worked up" , "Old woman" , "I worry" , "Pernickety person" , "Perfectionist" .)