Master Charlie’s little coat (3)
I believe the answer is:
mac
'coat' is the definition.
(mac is a kind of coat)
'master charlie's little' is the wordplay.
'master' becomes 'ma'.
'charlie's' becomes 'cs' (phonetic alphabet: alpha, bravo, charlie etc.).
'little' means to remove the last letter (the word is not quite complete).
'cs' with its final letter taken away is 'c'.
'ma'+'c'='MAC'
(Other definitions for mac that I've seen before include "It may help you keep dry" , "Overcoat" , "PC" , "laptop?" , "one used in shower?" .)