Dull drink on rather wet island avoided (7)

I believe the answer is:

humdrum

I'm a little stuck... Click here to teach me more about this clue!

'rather wet island avoided' is the definition.
I can't judge whether this defines the answer.

'dull drink on' is the wordplay.
'dull' becomes 'humd' (I've seen this in another clue).
'drink on' becomes 'rum' (rum is a kind of drink. I am not sure about the 'on' bit.).
'humd'+'rum'='HUMDRUM'

Can you help me to learn more?

(Other definitions for humdrum that I've seen before include "Droning sounds" , "Everyday, boring" , "Common place" , "Routine and monotonous" , "Ordinary - monotonous" .)

I've seen this clue in The Independent.

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