Host accepts a coat (3)
I believe the answer is:
mac
'coat' is the definition.
(mac is a kind of coat)
'host accepts a' is the wordplay.
'host' becomes 'mc' (I've seen this in other clues).
'accepts' means one lot of letters goes inside another.
'mc' placed around 'a' is 'MAC'.
(Other definitions for mac that I've seen before include "Waterproof coat (colloq.)" , "It may help you keep dry" , "laptop?" , "Coat - computer" , "A Gaelic son, often in name" .)