Excellent American officer gets jerk snorting whizz (9)
I believe the answer is:
copacetic
'excellent' is the definition.
(I've seen this before)
'american officer gets jerk snorting whizz' is the wordplay.
'american officer' becomes 'cop' (cop is a kind of officer. I am not sure about the 'american' bit.).
'gets' says to put letters next to each other.
'jerk' becomes 'tic' (jerking movement by the body).
'snorting' is an insertion indicator (snort can mean to ingest through the nose).
'whizz' becomes 'ace' (synonyms).
'cop'+'tic'='coptic'
'coptic' placed around 'ace' is 'COPACETIC'.
Can you help me to learn more?
(Another definition for copacetic that I've seen is " Excellent".)