Writers were emotional, upset by US jails (4-6,4)

I believe the answer is:

felt-tipped pens

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'us jails' is the definition.
I know nothing about this answer so I can't judge whether this works.

'writers were emotional upset by' is the wordplay.
'writers' becomes 'pens' (I've seen this before).
'were' becomes 'felt' (feeling is a kind of being).
'emotional upset' becomes 'tipped' (I've seen this in another clue. I am not sure about the 'emotional' bit.).
'by' says to put letters next to each other.
'felt'+'tipped'='felttipped'
'pens' after 'felttipped' is 'FELT-TIPPED PENS'.

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I've seen this clue in The Times.

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