I can't go off outer layer (7)

I believe the answer is:

coating

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'outer layer' is the definition.
'coating' can be an answer for 'layer' (I've seen this before). I am not certain of the 'outer' bit.

'i can't go off' is the wordplay.
'off' is an anagram indicator.
'i'+'cant'+'go'='icantgo'
'icantgo' with letters rearranged gives 'COATING'.

Can you help me to learn more?

(Other definitions for coating that I've seen before include "Thin layer; covering" , "Protective layer" , "film" .)

I've seen this clue in The Mirror.

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