Flier’s harmless mischief (4)

I believe the answer is:

lark

I believe this is a double definition.

'flier's' is the first definition.
(lark is a type of bird)

'harmless mischief' is the second definition.
(a lark is a bit of fun or mischief)

(Other definitions for lark that I've seen before include "Songbird - bit of fun" , "Small songbird or playful action" , "One singing high" , "Early bird with morning song" , "Songbird; escapade" .)

I've seen this clue in The Times.

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