Birds gripped, stuffing is awful (9)

I believe the answer is:

shelducks

I'm a little stuck... Click here to teach me more about this clue!

'birds' is the definition.
(shelduck is a kind of bird)

'gripped stuffing is awful' is the wordplay.
'gripped' becomes 'held' (I've seen this before).
'stuffing' is an insertion indicator.
'is awful' becomes 'sucks' (I am not sure about this - if you are sure you should believe this answer much more).
'held' placed inside 'sucks' is 'SHELDUCKS'.

Can you help me to learn more?

I've seen this clue in The Guardian.

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