Small winged insects covering old planes (7)

I believe the answer is:

smooths

'planes' is the definition.
(both can mean to make level)

'small winged insects covering old' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'winged insects' becomes 'moths'.
'covering' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'moths' going around 'o' is 'mooths'.
's'+'mooths'='SMOOTHS'

I've seen this clue in The Telegraph.

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