It's harmful, raising fists at experts (3,5)

'experts' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'it's harmful raising fists' is the wordplay.
'it's harmful' becomes 'bad' (similar in meaning).
'raising' shows that the letters should be reversed in order (in a down clue, letters go up).
'fists' becomes 'hands' (I can't explain this - if you can you should believe this answer much more).
'bad' reversed gives 'dab'.
'dab'+'hands'='DAB HANDS'

'at' acts as a link.

Can you help me to learn more?