Being a lout means nothing to a fathead (3)
I believe the answer is:
oaf
'a fathead' is the definition.
(I've seen this in another clue)
'being a lout means nothing' is the wordplay.
I cannot really see how this works, but
'a' is within the answer.
'nothing' could be 'o' (looks like zero - 0) and 'o' is found in the answer.
A single letter 'f' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for oaf that I've seen before include "Boor or lout" , "A clumsy or stupid person" , "Yahoo" , "buffoon" , "Idiot" .)