Collie fetched content willingly (4)

I believe the answer is:

lief

'willingly' is the definition.
(I've seen this in another clue)

'collie fetched content' is the wordplay.
'content' says the answer is hidden in the clue (letters contained within the clue).
'LIEF' is hidden within 'collie fetched'.

(Another definition for lief that I've seen is " In old usage, gladly or willingly - file away".)

I've seen this clue in The Telegraph.

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