How sly all may appear superficially (9)

I believe the answer is:

shallowly

'superficially' is the definition.
(thesaurus)

'how sly all may appear' is the wordplay.
'may appear' indicates an anagram (how the letters might appear in a different order).
'how'+'sly'+'all'='howslyall'
'howslyall' with letters rearranged gives 'SHALLOWLY'.

(Another definition for shallowly that I've seen is " In a superficial manner".)

I've seen this clue in The Globe and Mail.

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