Idiot slopes away with Mo (8)
I believe the answer is:
dipstick
'idiot' is the definition.
(informal term for a stupid person)
'slopes away with mo' is the wordplay.
'slopes away' becomes 'dips' (dipping is a kind of sloping. I am not sure about the 'away' bit.).
'with' says to put letters next to each other.
'mo' becomes 'tick' (both can mean a short amount of time).
'dips'+'tick'='DIPSTICK'
Can you help me to learn more?
(Other definitions for dipstick that I've seen before include "Engine oil measurer" , "Idiot" , "one concealed under bonnet?" , "help to motorist" , "Fool" .)