A danger to the people ahead of one (6)
I believe the answer is:
menace
'a danger' is the definition.
(menace is a kind of danger)
'the people ahead of one' is the wordplay.
'the people' becomes 'men' (man is a kind of person).
'ahead of' is a charade indicator (letters next to each other) (I've seen this in other clues).
'one' becomes 'ace' ('ace' can be a synonym of 'one').
'men'+'ace'='MENACE'
'to' is the link.
(Other definitions for menace that I've seen before include "Threaten with violence" , "Threat, danger" , "Harmful person" , "serious nuisance" , "Act in a threatening manner" .)