Clearly frightened, has played the card (7)

I believe the answer is:

shaking

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'clearly frightened' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs can sometimes define each other.

'has played the card' is the wordplay.
'played' indicates anagramming the letters.
'the card' becomes 'king' (type of playing card).
'has' anagrammed gives 'sha'.
'sha'+'king'='SHAKING'

Can you help me to learn more?

(Other definitions for shaking that I've seen before include "Atremble" , "Trembling, vibrating" .)

I've seen this clue in the Evening Standard.

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