Threaten people with a club, perhaps (6)
I believe the answer is:
menace
'threaten' is the definition.
(synonyms)
'people with a club perhaps' is the wordplay.
'people' becomes 'men' (men can refer to humanity as a whole).
'with' says to put letters next to each other.
'a club perhaps' becomes 'ace' (I can't justify this - if you can you should give a lot more credence to this answer).
'men'+'ace'='MENACE'
Can you help me to learn more?
(Other definitions for menace that I've seen before include "A source of danger" , "Serious threat" , "serious nuisance" , "Threat; threaten" , "ominous atmosphere" .)