After Chuck, perhaps Dennis blunders (7)
I believe the answer is:
bungles
'dennis blunders' is the definition.
'bungles' can be an answer for 'blunders' ('bungle' can be a synonym of 'blunder'). I'm not sure about the 'dennis' bit.
'after chuck perhaps' is the wordplay.
'after' is a charade indicator (letters next to each other).
'chuck' becomes 'bung'.
'perhaps' becomes 'les' (I can't justify this - if you can you should give a lot more credence to this answer).
'bung' next to 'les' is 'BUNGLES'.
Can you help me to learn more?
(Another definition for bungles that I've seen is " messes up".)