Coastguard leaving shore confused at no one returning for ceremony (10)
I believe the answer is:
graduation
'for ceremony' is the definition.
(graduation is a kind of ceremony)
'coastguard leaving shore confused at no one returning' is the wordplay.
I cannot quite understand how this works, but
'at' could be 'on' (location) and 'on' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for graduation that I've seen is " Successful completion of study".)