Whit Monday’s beginning with Charlie in disgrace (7)
I believe the answer is:
modicum
'whit' is the definition.
(thesaurus)
'monday's beginning with charlie in disgrace' is the wordplay.
'monday' becomes 'm'.
'beginning with' is a charade indicator (letters next to each other) (some letters go at the beginning of others).
'charlie' becomes 'C' (phonetic alphabet).
'in' is an insertion indicator.
'disgrace' becomes 'odium' (I've seen this in another clue).
'c' inserted into 'odium' is 'odicum'.
'm'+'odicum'='MODICUM'
(Other definitions for modicum that I've seen before include "touch" , "I cod Mum into providing a small quantity" , "Little bit" , "A small amount as of drink" , "Token amount" .)