Edgy and unguarded, not having some sleep leads to irritation for babies (5,4)
I believe the answer is:
nappy rash
'edgy and unguarded not having some' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'sleep leads to irritation for babies' is the wordplay.
I cannot quite see how this works, but
'sleep' could be 'nap' (a nap is a short sleep) and 'nap' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nappy rash that I've seen before include "wet spots" , "Baby's discomfort" .)