Tease America to turn up sweetener (5)
I believe the answer is:
sugar
'sweetener' is the definition.
(I know that sugar is a type of sweetener)
'tease america to turn up' is the wordplay.
'tease' becomes 'rag' (synonyms).
'america' becomes 'US' (United States).
'to turn up' shows that the letters should be reversed in order.
'rag'+'us'='ragus'
'ragus' back-to-front is 'SUGAR'.
(Other definitions for sugar that I've seen before include "Common sweetener" , "Sweeten" , "Damn" , "Make more palatable" , "rotter!" .)