A child will be if his parents are late (8)
I believe the answer is:
orphaned
'if his parents are late' is the definition.
The definition suggests a singular noun but the answer is not.
'a child will' is the wordplay.
'a child' becomes 'orphan' (orphan is a kind of child).
'will' becomes 'ed' (I can't justify this - if you can you should believe this answer much more).
'orphan'+'ed'='ORPHANED'
'be' acts as a link.
Can you help me to learn more?
(Other definitions for orphaned that I've seen before include "Left without father or mother" , "Having both parents dead" .)