Insult making little impression... (6)
I believe the answer is:
slight
'insult' is the definition.
(I've seen this before)
'little impression' is the wordplay.
I cannot quite see how this works, but
'little' could be 'l' (abbreviation for little) and 'l' is present in the answer.
The remaining letters 'sight' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'making' is the link.
Can you help me to learn more?
(Other definitions for slight that I've seen before include "Flimsy, tenuous" , "Redeemer" , "Deliberate discourteous act" , "Insignificant, flimsy" , "Slim or tenuous" .)