Apple disheartened by this device? (5)
I believe the answer is:
corer
'apple disheartened by this device?' is the definition.
The definition suggests a singular noun which matches the answer.
'apple disheartened by this device?' is the wordplay.
'apple' becomes 'eater' (I've seen this before).
'disheartened' means to remove the middle letters (the middle or heart is removed).
'by' means one lot of letters go next to another.
'this device?' becomes 'cor' (I am not sure about this - if you are sure you should believe this answer much more).
'eater' with its centre taken out is 'er'.
'er' put after 'cor' is 'CORER'.
Can you help me to learn more?
(Other definitions for corer that I've seen before include "kitchen implement?" , "(Eg, apple) cutter" , "Device used on apples" .)