Cleaner to hearten lady? Quite the opposite (9)
'cleaner' is the definition.
(detergent is a kind of cleaner)
'hearten lady? quite the opposite' is the wordplay.
I cannot really see how this works, but
'lady?' could be 'de' and 'de' is located in the answer.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for detergent that I've seen before include "Soluble cleanser" , "Synthetic cleaning substance for washing machines" , "help with the washing-up" , "Soapless cleanser" , "cleaner" .)
'cleaner to hearten' is the definition.
I can't judge whether this defines the answer.
'lady? quite the opposite' is the wordplay.
'lady?' becomes 'de'.
'quite the opposite' becomes 'ter' (I can't justify this - if you can you should believe this answer much more).
'de'+'ter'='DETER'
(Other definitions for deter that I've seen before include "Cause not to do something" , "Daunt" , "Frighten off; prevent" , "Put (someone) off" , "Discourage through fear of consequences" .)