Lag is ale nut under the influence (8)

I believe the answer is:

insulate

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'lag' is the definition.
(I've seen this before)

'is ale nut under the influence' is the wordplay.
'is ale nut' can be anagrammed to 'INSULATE'.
But, I'm not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for insulate that I've seen before include "Thermally protect" , "Cover or protect with a utensil (8)" , "Cocoon" , "Cover with material to prevent loss of heat" , "Lean suit (anag.)" .)

I've seen this clue in The Sun.

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