Takes clip out of hair, perhaps, and fails to meet expectations (4,4)

I believe the answer is:

lets down

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'hair perhaps and fails to meet expectations' is the definition.
I can't judge whether this definition defines the answer.

'takes clip out' is the wordplay.
'takes clip' becomes 'lets' (I can't explain this - if you can you should believe this answer much more).
'out' becomes 'down' (similar in meaning).
'lets'+'down'='LETS DOWN'

'of' acts as a link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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