Homeless child with a condition (4)
I believe the answer is:
waif
'homeless child' is the definition.
(I've seen this before)
'with a condition' is the wordplay.
'with' becomes 'w' (abbreviation).
'condition' becomes 'if' (as in 'a big if').
'w'+'a'+'if'='WAIF'
(Other definitions for waif that I've seen before include "Neglected, homeless child" , "Gamin" , "neglected issue" , "Ragamuffin" , "Homeless child - thin person" .)