Score with an acidic, sweet chestnut essence (4)
I believe the answer is:
'score' is the definition.
(etch can mean to score or carve into something)
'an acidic sweet chestnut essence' is the wordplay.
'ETCH' is hidden within the letters.
But, I'm not sure how this is indicated.
'with' is the link.
Can you help me to learn more?
(Other definitions for etch that I've seen before include "Make picture by engraving metal" , "Design on metal or glass using acid" , "Carve into surface, impress deeply" , "Corrode" , "Cut design onto metal using acid" .)