Potential fly-by-night's below royal rank (6,4)

I believe the answer is:

woolly bear

'potential fly-by-night's' is the definition.
(caterpillars may become moths or 'fly-by-nights')

'below royal rank' is the wordplay.
'rank' is an anagram indicator.
'below'+'royal'='belowroyal'
'belowroyal' with letters rearranged gives 'WOOLLY BEAR'.

I've seen this clue in The Guardian.

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