May heartless son dwarf me (6)
I believe the answer is:
myself
'me' is the definition.
(I've seen this in another clue)
'may heartless son dwarf' is the wordplay.
'heartless' suggests removing the centre.
'son' becomes 's' (genealogical abbreviation for son).
'dwarf' becomes 'elf' (I've seen this before).
'may' with its centre removed is 'my'.
'my'+'s'+'elf'='MYSELF'
(Other definitions for myself that I've seen before include "Me, in person" , "Crossword compiler" , "I personally" , "Emphatically, me" , "Reflexive pronoun" .)