Mere daydream, but vicar’s drifted off (4)

I believe the answer is:

erie

'mere' is the definition.
(mere can mean a lake eg Lake Erie)

I can't explain the remainder of the clue.

(Other definitions for erie that I've seen before include "Buffalo's lake" , "North american lake sounds spooky" , "Great lake in Eire" , "One of the Great Lakes" , "N. American lake" .)

I've seen this clue in The Times.

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