Speaker’s set of notes lacking heart (5)
I believe the answer is:
cored
'speaker's set' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives occasionally define each other.
'notes lacking heart' is the wordplay.
I cannot quite see how this works, but
'notes' could be 'ed' and 'ed' is present in the answer.
'heart' could be 'cor' (I've seen this in another clue) and 'cor' is found within the answer.
No letters remain.
This explanation may well be incorrect...
'of' is the link.
(Other definitions for cored that I've seen before include "disheartened" , "having something at heart" , "Removed centre from apple for dicor" , "With central part removed" , "dispensed with the centre" .)