Coastal town drunk heading off on a cloudy midday (9)

'coastal town drunk heading off' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'on a cloudy midday' is the wordplay.
'on' means one lot of letters goes inside another (as in clothing 'on' a person).
'cloudy' becomes 'dull' (I've seen this before).
'midday' becomes 'ulla' (I can't justify this - if you can you should give a lot more credence to this answer).
'a'+'dull'='adull'
'adull' inserted inside 'ulla' is 'ULLADULLA'.

Can you help me to learn more?