Pries into one's other son (5)
I believe the answer is:
noses
'pries' is the definition.
('nose' can be a synonym of 'pry')
'into one's other son' is the wordplay.
'into' is an insertion indicator.
'other' is an anagram indicator.
'son' becomes 's' (genealogical abbreviation for son).
'ones' anagrammed gives 'noes'.
'noes' going around 's' is 'NOSES'.
(Other definitions for noses that I've seen before include "Hooters" , "Beaks, conks" , "Snouts" , "Schnozzles" , "Organs of smell" .)