By leaving a person with no heir? (3)
I believe the answer is:
per
'by' is the definition.
(I've seen this in another clue)
'person with no heir?' is the wordplay.
'with no' is a deletion indicator.
'heir?' becomes 'son' (I've seen this before).
'person' with 'son' taken away is 'PER'.
'leaving a' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for per that I've seen before include "Preposition meaning for each" , "According to" , "For each or every" , "Preposition indicating by means of" .)