For each childless person (3)
I believe the answer is:
per
This could be a double definition.
'for each' is the first definition.
('per' can mean for each)
'childless person' is the second definition.
'per' can be an answer for 'person' (abbreviation). I am unsure of the 'childless' bit.
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" .)