Idiot anticipating trouble leading to attack (6)
I believe the answer is:
assail
'attack' is the definition.
('assail' can be a synonym of 'attack')
'idiot anticipating trouble' is the wordplay.
'idiot' becomes 'ass' (I've seen this before).
'anticipating' means one lot of letters go next to another.
'trouble' becomes 'ail' ('ail' can be a synonym of 'trouble').
'ass'+'ail'='ASSAIL'
'leading to' is the link.
(Other definitions for assail that I've seen before include "Sudden attack" , "Charge" , "Go for" , "Trouble" , "Maybe mug" .)