Sham food? (4)

I believe the answer is:

mash

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'food?' is the definition.
(mashed potato)

'sham' is the wordplay.
'sham' can be anagrammed to 'MASH'.
Though, I'm not clear how this is indicated.

Can you help me to learn more?

(Other definitions for mash that I've seen before include "Pummel" , "Crush, potatoes say" , "Bangers' frequent partner?" , "Brew or infuse (tea)" , "TV series" .)

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