Tasteless rubbish! American! I'm off! (2-2)
I believe the answer is:
ta-ta
'i'm off' is the definition.
I can't tell whether this defines the answer.
'tasteless rubbish american' is the wordplay.
'tasteless rubbish' becomes 'tat' (I've seen this before).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'tat'+'a'='TA-TA'
Can you help me to learn more?
(Other definitions for ta-ta that I've seen before include "Bye!" , "Cheerio" , "A Farewell" , "Bye-bye" , "Adieu" .)