Filling operation includes jargon (5)

I believe the answer is:

lingo

'jargon' is the definition.
(I know that jargon can be written as lingo)

'filling operation includes' is the wordplay.
'includes' indicates a hidden word.
'LINGO' is hidden within 'filling operation'.

(Other definitions for lingo that I've seen before include "Language (slang)" , "Unfamiliar language or jargon" , "strange language" , "French?" , "Jargon, language (colloq.)" .)

I've seen this clue in The Daily Express.

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