More than one chap, expert, providing this threat (6)
I believe the answer is:
menace
'this threat' is the definition.
(synonyms)
'more than one chap expert' is the wordplay.
'more than one chap' becomes 'men' (more than one man).
'expert' becomes 'ace' (ace can informally mean very good).
'men'+'ace'='MENACE'
'providing' acts as a link.
(Other definitions for menace that I've seen before include "Act in a threatening manner" , "peril" , "A source of danger" , "Serious threat" , "Threat, show of hostility" .)