No material envelops loud American (7)
I believe the answer is:
refusal
'no' is the definition.
(refusing is saying no)
'material envelops loud american' is the wordplay.
'material' becomes 'real' (associated in meaning).
'envelops' is an insertion indicator (I've seen this in other clues).
'loud' becomes 'f' (short for forte - 'loud' in music).
'american' becomes 'US' (United States).
'f'+'us'='fus'
'real' placed around 'fus' is 'REFUSAL'.
(Other definitions for refusal that I've seen before include "regrets?" , "fault in the show ring" , "Turning-down; denial" , "Non-acceptance" , "Stop by fence" .)