Guys with power in top grade were dangerous (8)
I believe the answer is:
menacing
'dangerous' is the definition.
(thesaurus)
'guys with power in top grade' is the wordplay.
'guys' becomes 'men' (guy can mean a man).
'with' means one lot of letters go next to another.
'power' becomes 'ac' (AC is an example).
'top' says to take the initial letters.
The initial letter of 'grade' is 'g'.
'men'+'ac'+'in'+'g'='MENACING'
'were' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for menacing that I've seen before include "Scary" , "Suggesting danger" , "Intimidating" , "Ominous" , "Threatening" .)