Will not show the usual custom (4)
I believe the answer is:
wont
'custom' is the definition.
(I know that wont is a type of custom)
'will not show the usual' is the wordplay.
I cannot really understand how this works, but
an anagram of 'not' is 'ont' which is within the answer.
A single letter 'w' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for wont that I've seen before include "Succinct refusal" , "Is not going to" , "Action habitually associated with someone" , "Accustomed" , "customary behaviour" .)