Love child maybe painful to bring up (4)
I believe the answer is:
eros
'love child maybe' is the definition.
(god of love sometimes depicted as a child)
'painful to bring up' is the wordplay.
'painful' becomes 'sore' (synonyms).
'to bring up' says the letters should be written in reverse (I've seen 'brought up' mean this (in a down clue, letters go up)).
'sore' reversed gives 'EROS'.
(Other definitions for eros that I've seen before include "Winged god of love" , "Greek love-god" , "Cupid's Greek alternative" , "Famous statue in Piccadilly, London" , "capital statue" .)