Parent filled with concerning, foreboding feeling (5)
I believe the answer is:
dread
'foreboding feeling' is the definition.
'dread' can be an answer for 'feeling' (dread is a kind of feeling). I am not sure about the 'foreboding' bit.
'parent filled with concerning' is the wordplay.
'parent' becomes 'dad' (dad can informally mean father).
'filled with' means one lot of letters goes inside another.
'concerning' becomes 're' (both can mean on a particular topic).
'dad' enclosing 're' is 'DREAD'.
Can you help me to learn more?
(Other definitions for dread that I've seen before include "great anxiety" , "quail" , "Adder (anag)" , "fright" , "Hairstyle" .)