Group ready with Charlie (4)
I believe the answer is:
sect
'group' is the definition.
(I've seen this in other clues)
'ready with charlie' is the wordplay.
'ready' becomes 'set' ('set' can be similar in meaning to 'ready').
'with' is an insertion indicator.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'set' enclosing 'c' is 'SECT'.
(Other definitions for sect that I've seen before include "Denomination" , "Small group with own religious beliefs" , "Subdivision of a larger religious group" , "Cult group" , "Group of people with unusual religious beliefs" .)