For every boy there's somebody (6)
I believe the answer is:
person
'somebody' is the definition.
(I've seen this in another clue)
'for every boy' is the wordplay.
'for every' becomes 'per' ('per' means 'for each' or 'for every').
'boy' becomes 'son' (synonyms).
'per'+'son'='PERSON'
'there's' acts as a link.
(Other definitions for person that I've seen before include "anyone else" , "Bod" , "A man or woman" , "See 17" , "Individual human being" .)