An American tier sounded grim (7)
I believe the answer is:
austere
'grim' is the definition.
(I've seen this before)
'an american tier sounded' is the wordplay.
I cannot quite understand how this works, but
'an' could be 'a' and 'a' is present in the answer.
'american' could be 'us' (abbreviation for United States) and 'us' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for austere that I've seen before include "Spartan and abstemious" , "Severe; lacking luxuries" , "Severe or strict in attitude" , "Severely simple and plain in appearance" , "severely self-disciplined" .)