Plants gun, if deceitful (5)

I believe the answer is:

fungi

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

'plants' is the definition.
(fungus is a kind of plant)

'gun if deceitful' is the wordplay.
'gun if' can be anagrammed to 'FUNGI'.
However, I'm not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for fungi that I've seen before include "rusts?" , "woodland feature" , "Spore-producing organisms" , "Toadstools, say" , "life in woodland?" .)

I've seen this clue in The Guardian.

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