The answer to this lies in the retort (6)
I believe the answer is:
hereto
'the answer to this lies' is the definition.
The definition and answer are not the same part of speech.
'in the retort' is the wordplay.
'in' indicates a hidden word.
'HERETO' can be found hidden inside 'the retort'.
Can you help me to learn more?
(Other definitions for hereto that I've seen before include "To this point or time (6" , "object" , "To this writing or document, in legalese" , "(Appended) to this document" , "In this direction" .)