Fruit lose heart when cook uses it (5)
I believe the answer is:
corer
'it' is the definition.
The definition suggests a singular noun which matches the answer.
'fruit lose heart when cook' is the wordplay.
I cannot quite see how this works, but
'heart' could be 'cor' (I've seen this in another clue) and 'cor' is found in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is found within the answer.
A single letter 'r' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'uses' is the link.
Can you help me to learn more?
(Other definitions for corer that I've seen before include "(Eg, apple) cutter" , "Device used on apples" , "kitchen implement?" .)