Crossword Genius

Nucleus of bigger machine (4)

Ross

I believe the answer is:

germ

'nucleus' is the definition.
(thesaurus)

'of bigger machine' is the wordplay.
'of' indicates a hidden word.
'GERM' is hidden in the letters of 'bigger machine'.

(Other definitions for germ that I've seen before include "Cause of some diseases" , "Microorganism causing disease" , "starting point" , "Bug" , "virus?" .)

I've seen this clue in The Mirror.
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