Small matter for an associate of Dick and Harry (4)
I believe the answer is:
atom
'small matter' is the definition.
'for an associate of dick and harry' is the wordplay.
I cannot really understand how this works, but
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is found within the answer.
'an' could be 'a' and 'a' is found within the answer.
A single letter 'm' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for atom that I've seen before include "Piece of matter in moat" , "Neutron and proton" , "type of bomb" , "An explosive particle as in bomb" , "Tiny bit" .)