Wrongly inform of fog finally clearing on harbour (9)
I believe the answer is:
misreport
'wrongly inform of fog finally' is the definition.
I can't tell whether this defines the answer.
'clearing on harbour' is the wordplay.
'clearing' becomes 'mis' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' becomes 're' ('on' can be mean 'with reference to').
'harbour' becomes 'port' (I've seen this before).
'mis'+'re'+'port'='MISREPORT'
Can you help me to learn more?
(Other definitions for misreport that I've seen before include "falsify accounts" , "Give false information" .)