Guard's wayward daughter dismissed sweetener (5)
I believe the answer is:
sugar
'sweetener' is the definition.
(I know that sugar is a type of sweetener)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for sugar that I've seen before include "e.g. Glucose" , "Plantation product" , "Argus (anag.)" , "rotter!" , "--- Ray Robinson, boxer" .)