Credulous on hearing excuse for being late? (4-4)
I believe the answer is:
wide-eyed
'credulous' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for wide-eyed that I've seen before include "Showing great surprise" , "Inexperienced; showing amazement" , "Innocent - believing" .)