It quivers, similar to a swan (5)

I believe the answer is:

aspen

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'it quivers' is the definition.
The definition suggests a singular noun which matches the answer.

'similar to a swan' is the wordplay.
'similar to' becomes 'as'.
'a swan' becomes 'pen' (pen is a kind of swan).
'as'+'pen'='ASPEN'

Can you help me to learn more?

(Other definitions for aspen that I've seen before include "somewhere in Colorado" , "Its leaves flutter in the slightest breeze" , "Panes (anag.)" , "Colorado winter sports town" , "One trembling" .)

I've seen this clue in The Guardian.

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