Silly achievement gets that woman hit over the head (14)

I believe the answer is:

featherbrained

'silly' is the definition.
(synonyms)

'achievement gets that woman hit over the head' is the wordplay.
'achievement' becomes 'feat' (feat is a kind of achievement).
'gets' means one lot of letters go next to another.
'that woman' becomes 'her' ('her' refers to a woman).
'hit over the head' becomes 'brained'.
'feat'+'her'+'brained'='FEATHERBRAINED'

(Another definition for featherbrained that I've seen is " Dizzy".)

I've seen this clue in The Daily Express.

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