Sweetening top paid off - tasty (5)
I believe the answer is:
sapid
'tasty' is the definition.
(I've seen this in another clue)
'sweetening top paid off' is the wordplay.
'top' says to take the initial letters.
'off' indicates an anagram.
The first letter of 'sweetening' is 's'.
'paid' anagrammed gives 'apid'.
's'+'apid'='SAPID'
(Other definitions for sapid that I've seen before include "excellent taste" , "Pleasant tasting" , "Full of flavour" , "Interesting" , "Tasty" .)