Fly-by-night revealed by parent without hesitation (4)
I believe the answer is:
moth
'fly-by-night' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'parent without hesitation' is the wordplay.
'parent' becomes 'mother' (type of parent).
'without' suggests deleting specific letters.
'hesitation' becomes 'er' (sound made while hesitating - um, er).
'mother' with 'er' removed is 'MOTH'.
'revealed by' is the link.
Can you help me to learn more?
(Other definitions for moth that I've seen before include "Cloth-eating insect" , "one drawn to the bright lights" , "Night flying insect" , "Fairy like 13" , "Usually nocturnal insect" .)